Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2567 insertions, 0 deletions

diff --git a/intl/icu/source/i18n/unicode/calendar.h b/intl/icu/source/i18n/unicode/calendar.h
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+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+********************************************************************************
+*   Copyright (C) 1997-2014, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+********************************************************************************
+*
+* File CALENDAR.H
+*
+* Modification History:
+*
+*   Date        Name        Description
+*   04/22/97    aliu        Expanded and corrected comments and other header
+*                           contents.
+*   05/01/97    aliu        Made equals(), before(), after() arguments const.
+*   05/20/97    aliu        Replaced fAreFieldsSet with fAreFieldsInSync and
+*                           fAreAllFieldsSet.
+*   07/27/98    stephen     Sync up with JDK 1.2
+*   11/15/99    weiv        added YEAR_WOY and DOW_LOCAL
+*                           to EDateFields
+*    8/19/2002  srl         Removed Javaisms
+*   11/07/2003  srl         Update, clean up documentation.
+********************************************************************************
+*/
+
+#ifndef CALENDAR_H
+#define CALENDAR_H
+
+#include "unicode/utypes.h"
+
+#if U_SHOW_CPLUSPLUS_API
+
+/**
+ * \file
+ * \brief C++ API: Calendar object
+ */
+#if !UCONFIG_NO_FORMATTING
+
+#include "unicode/uobject.h"
+#include "unicode/locid.h"
+#include "unicode/timezone.h"
+#include "unicode/ucal.h"
+#include "unicode/umisc.h"
+
+U_NAMESPACE_BEGIN
+
+class ICUServiceFactory;
+
+// Do not conditionalize the following with #ifndef U_HIDE_INTERNAL_API,
+// it is a return type for a virtual method (@internal)
+/**
+ * @internal
+ */
+typedef int32_t UFieldResolutionTable[12][8];
+
+class BasicTimeZone;
+/**
+ * `Calendar` is an abstract base class for converting between
+ * a `UDate` object and a set of integer fields such as
+ * `YEAR`, `MONTH`, `DAY`, `HOUR`, and so on.
+ * (A `UDate` object represents a specific instant in
+ * time with millisecond precision. See UDate
+ * for information about the `UDate` class.)
+ *
+ * Subclasses of `Calendar` interpret a `UDate`
+ * according to the rules of a specific calendar system.
+ * The most commonly used subclass of `Calendar` is
+ * `GregorianCalendar`. Other subclasses could represent
+ * the various types of lunar calendars in use in many parts of the world.
+ *
+ * **NOTE**: (ICU 2.6) The subclass interface should be considered unstable -
+ * it WILL change.
+ *
+ * Like other locale-sensitive classes, `Calendar` provides a
+ * static method, `createInstance`, for getting a generally useful
+ * object of this type. `Calendar`'s `createInstance` method
+ * returns the appropriate `Calendar` subclass whose
+ * time fields have been initialized with the current date and time:
+ *
+ *     Calendar *rightNow = Calendar::createInstance(errCode);
+ *
+ * A `Calendar` object can produce all the time field values
+ * needed to implement the date-time formatting for a particular language
+ * and calendar style (for example, Japanese-Gregorian, Japanese-Traditional).
+ *
+ * When computing a `UDate` from time fields, some special circumstances
+ * may arise: there may be insufficient information to compute the
+ * `UDate` (such as only year and month but no day in the month),
+ * there may be inconsistent information (such as "Tuesday, July 15, 1996"
+ * -- July 15, 1996 is actually a Monday), or the input time might be ambiguous
+ * because of time zone transition.
+ *
+ * **Insufficient information.** The calendar will use default
+ * information to specify the missing fields. This may vary by calendar; for
+ * the Gregorian calendar, the default for a field is the same as that of the
+ * start of the epoch: i.e., YEAR = 1970, MONTH = JANUARY, DATE = 1, etc.
+ *
+ * **Inconsistent information.** If fields conflict, the calendar
+ * will give preference to fields set more recently. For example, when
+ * determining the day, the calendar will look for one of the following
+ * combinations of fields.  The most recent combination, as determined by the
+ * most recently set single field, will be used.
+ *
+ *     MONTH + DAY_OF_MONTH
+ *     MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
+ *     MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
+ *     DAY_OF_YEAR
+ *     DAY_OF_WEEK + WEEK_OF_YEAR
+ *
+ * For the time of day:
+ *
+ *     HOUR_OF_DAY
+ *     AM_PM + HOUR
+ *
+ * **Ambiguous Wall Clock Time.** When time offset from UTC has
+ * changed, it produces an ambiguous time slot around the transition. For example,
+ * many US locations observe daylight saving time. On the date switching to daylight
+ * saving time in US, wall clock time jumps from 12:59 AM (standard) to 2:00 AM
+ * (daylight). Therefore, wall clock time from 1:00 AM to 1:59 AM do not exist on
+ * the date. When the input wall time fall into this missing time slot, the ICU
+ * Calendar resolves the time using the UTC offset before the transition by default.
+ * In this example, 1:30 AM is interpreted as 1:30 AM standard time (non-exist),
+ * so the final result will be 2:30 AM daylight time.
+ *
+ * On the date switching back to standard time, wall clock time is moved back one
+ * hour at 2:00 AM. So wall clock time from 1:00 AM to 1:59 AM occur twice. In this
+ * case, the ICU Calendar resolves the time using the UTC offset after the transition
+ * by default. For example, 1:30 AM on the date is resolved as 1:30 AM standard time.
+ *
+ * Ambiguous wall clock time resolution behaviors can be customized by Calendar APIs
+ * {@link #setRepeatedWallTimeOption} and {@link #setSkippedWallTimeOption}.
+ * These methods are available in ICU 49 or later versions.
+ *
+ * **Note:** for some non-Gregorian calendars, different
+ * fields may be necessary for complete disambiguation. For example, a full
+ * specification of the historical Arabic astronomical calendar requires year,
+ * month, day-of-month *and* day-of-week in some cases.
+ *
+ * **Note:** There are certain possible ambiguities in
+ * interpretation of certain singular times, which are resolved in the
+ * following ways:
+ *
+ *   1. 24:00:00 "belongs" to the following day. That is,
+ *      23:59 on Dec 31, 1969 < 24:00 on Jan 1, 1970 < 24:01:00 on Jan 1, 1970
+ *   2. Although historically not precise, midnight also belongs to "am",
+ *      and noon belongs to "pm", so on the same day,
+ *      12:00 am (midnight) < 12:01 am, and 12:00 pm (noon) < 12:01 pm
+ *
+ * The date or time format strings are not part of the definition of a
+ * calendar, as those must be modifiable or overridable by the user at
+ * runtime. Use `DateFormat` to format dates.
+ *
+ * `Calendar` provides an API for field "rolling", where fields
+ * can be incremented or decremented, but wrap around. For example, rolling the
+ * month up in the date December 12, **1996** results in
+ * January 12, **1996**.
+ *
+ * `Calendar` also provides a date arithmetic function for
+ * adding the specified (signed) amount of time to a particular time field.
+ * For example, subtracting 5 days from the date `September 12, 1996`
+ * results in `September 7, 1996`.
+ *
+ * ***Supported range***
+ *
+ * The allowable range of `Calendar` has been narrowed. `GregorianCalendar` used
+ * to attempt to support the range of dates with millisecond values from
+ * `Long.MIN_VALUE` to `Long.MAX_VALUE`. The new `Calendar` protocol specifies the
+ * maximum range of supportable dates as those having Julian day numbers
+ * of `-0x7F000000` to `+0x7F000000`. This corresponds to years from ~5,800,000 BCE
+ * to ~5,800,000 CE. Programmers should use the protected constants in `Calendar` to
+ * specify an extremely early or extremely late date.
+ *
+ * <p>
+ * The Japanese calendar uses a combination of era name and year number.
+ * When an emperor of Japan abdicates and a new emperor ascends the throne,
+ * a new era is declared and year number is reset to 1. Even if the date of
+ * abdication is scheduled ahead of time, the new era name might not be
+ * announced until just before the date. In such case, ICU4C may include
+ * a start date of future era without actual era name, but not enabled
+ * by default. ICU4C users who want to test the behavior of the future era
+ * can enable the tentative era by:
+ * <ul>
+ * <li>Environment variable <code>ICU_ENABLE_TENTATIVE_ERA=true</code>.</li>
+ * </ul>
+ *
+ * @stable ICU 2.0
+ */
+class U_I18N_API Calendar : public UObject {
+public:
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * Field IDs for date and time. Used to specify date/time fields. ERA is calendar
+     * specific. Example ranges given are for illustration only; see specific Calendar
+     * subclasses for actual ranges.
+     * @deprecated ICU 2.6. Use C enum UCalendarDateFields defined in ucal.h
+     */
+    enum EDateFields {
+#ifndef U_HIDE_DEPRECATED_API
+/*
+ * ERA may be defined on other platforms. To avoid any potential problems undefined it here.
+ */
+#ifdef ERA
+#undef ERA
+#endif
+        ERA,                  // Example: 0..1
+        YEAR,                 // Example: 1..big number
+        MONTH,                // Example: 0..11
+        WEEK_OF_YEAR,         // Example: 1..53
+        WEEK_OF_MONTH,        // Example: 1..4
+        DATE,                 // Example: 1..31
+        DAY_OF_YEAR,          // Example: 1..365
+        DAY_OF_WEEK,          // Example: 1..7
+        DAY_OF_WEEK_IN_MONTH, // Example: 1..4, may be specified as -1
+        AM_PM,                // Example: 0..1
+        HOUR,                 // Example: 0..11
+        HOUR_OF_DAY,          // Example: 0..23
+        MINUTE,               // Example: 0..59
+        SECOND,               // Example: 0..59
+        MILLISECOND,          // Example: 0..999
+        ZONE_OFFSET,          // Example: -12*U_MILLIS_PER_HOUR..12*U_MILLIS_PER_HOUR
+        DST_OFFSET,           // Example: 0 or U_MILLIS_PER_HOUR
+        YEAR_WOY,             // 'Y' Example: 1..big number - Year of Week of Year
+        DOW_LOCAL,            // 'e' Example: 1..7 - Day of Week / Localized
+
+        EXTENDED_YEAR,
+        JULIAN_DAY,
+        MILLISECONDS_IN_DAY,
+        IS_LEAP_MONTH,
+
+        FIELD_COUNT = UCAL_FIELD_COUNT // See ucal.h for other fields.
+#endif /* U_HIDE_DEPRECATED_API */
+    };
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+#ifndef U_HIDE_DEPRECATED_API
+    /**
+     * Useful constant for days of week. Note: Calendar day-of-week is 1-based. Clients
+     * who create locale resources for the field of first-day-of-week should be aware of
+     * this. For instance, in US locale, first-day-of-week is set to 1, i.e., SUNDAY.
+     * @deprecated ICU 2.6. Use C enum UCalendarDaysOfWeek defined in ucal.h
+     */
+    enum EDaysOfWeek {
+        SUNDAY = 1,
+        MONDAY,
+        TUESDAY,
+        WEDNESDAY,
+        THURSDAY,
+        FRIDAY,
+        SATURDAY
+    };
+
+    /**
+     * Useful constants for month. Note: Calendar month is 0-based.
+     * @deprecated ICU 2.6. Use C enum UCalendarMonths defined in ucal.h
+     */
+    enum EMonths {
+        JANUARY,
+        FEBRUARY,
+        MARCH,
+        APRIL,
+        MAY,
+        JUNE,
+        JULY,
+        AUGUST,
+        SEPTEMBER,
+        OCTOBER,
+        NOVEMBER,
+        DECEMBER,
+        UNDECIMBER
+    };
+
+    /**
+     * Useful constants for hour in 12-hour clock. Used in GregorianCalendar.
+     * @deprecated ICU 2.6. Use C enum UCalendarAMPMs defined in ucal.h
+     */
+    enum EAmpm {
+        AM,
+        PM
+    };
+#endif  /* U_HIDE_DEPRECATED_API */
+
+    /**
+     * destructor
+     * @stable ICU 2.0
+     */
+    virtual ~Calendar();
+
+    /**
+     * Create and return a polymorphic copy of this calendar.
+     *
+     * @return    a polymorphic copy of this calendar.
+     * @stable ICU 2.0
+     */
+    virtual Calendar* clone() const = 0;
+
+    /**
+     * Creates a Calendar using the default timezone and locale. Clients are responsible
+     * for deleting the object returned.
+     *
+     * @param success  Indicates the success/failure of Calendar creation. Filled in
+     *                 with U_ZERO_ERROR if created successfully, set to a failure result
+     *                 otherwise. U_MISSING_RESOURCE_ERROR will be returned if the resource data
+     *                 requests a calendar type which has not been installed.
+     * @return         A Calendar if created successfully. nullptr otherwise.
+     * @stable ICU 2.0
+     */
+    static Calendar* U_EXPORT2 createInstance(UErrorCode& success);
+
+    /**
+     * Creates a Calendar using the given timezone and the default locale.
+     * The Calendar takes ownership of zoneToAdopt; the
+     * client must not delete it.
+     *
+     * @param zoneToAdopt  The given timezone to be adopted.
+     * @param success      Indicates the success/failure of Calendar creation. Filled in
+     *                     with U_ZERO_ERROR if created successfully, set to a failure result
+     *                     otherwise.
+     * @return             A Calendar if created successfully. nullptr otherwise.
+     * @stable ICU 2.0
+     */
+    static Calendar* U_EXPORT2 createInstance(TimeZone* zoneToAdopt, UErrorCode& success);
+
+    /**
+     * Creates a Calendar using the given timezone and the default locale.  The TimeZone
+     * is _not_ adopted; the client is still responsible for deleting it.
+     *
+     * @param zone  The timezone.
+     * @param success      Indicates the success/failure of Calendar creation. Filled in
+     *                     with U_ZERO_ERROR if created successfully, set to a failure result
+     *                     otherwise.
+     * @return             A Calendar if created successfully. nullptr otherwise.
+     * @stable ICU 2.0
+     */
+    static Calendar* U_EXPORT2 createInstance(const TimeZone& zone, UErrorCode& success);
+
+    /**
+     * Creates a Calendar using the default timezone and the given locale.
+     *
+     * @param aLocale  The given locale.
+     * @param success  Indicates the success/failure of Calendar creation. Filled in
+     *                 with U_ZERO_ERROR if created successfully, set to a failure result
+     *                 otherwise.
+     * @return         A Calendar if created successfully. nullptr otherwise.
+     * @stable ICU 2.0
+     */
+    static Calendar* U_EXPORT2 createInstance(const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Creates a Calendar using the given timezone and given locale.
+     * The Calendar takes ownership of zoneToAdopt; the
+     * client must not delete it.
+     *
+     * @param zoneToAdopt  The given timezone to be adopted.
+     * @param aLocale      The given locale.
+     * @param success      Indicates the success/failure of Calendar creation. Filled in
+     *                     with U_ZERO_ERROR if created successfully, set to a failure result
+     *                     otherwise.
+     * @return             A Calendar if created successfully. nullptr otherwise.
+     * @stable ICU 2.0
+     */
+    static Calendar* U_EXPORT2 createInstance(TimeZone* zoneToAdopt, const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Gets a Calendar using the given timezone and given locale.  The TimeZone
+     * is _not_ adopted; the client is still responsible for deleting it.
+     *
+     * @param zone         The given timezone.
+     * @param aLocale      The given locale.
+     * @param success      Indicates the success/failure of Calendar creation. Filled in
+     *                     with U_ZERO_ERROR if created successfully, set to a failure result
+     *                     otherwise.
+     * @return             A Calendar if created successfully. nullptr otherwise.
+     * @stable ICU 2.0
+     */
+    static Calendar* U_EXPORT2 createInstance(const TimeZone& zone, const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Returns a list of the locales for which Calendars are installed.
+     *
+     * @param count  Number of locales returned.
+     * @return       An array of Locale objects representing the set of locales for which
+     *               Calendars are installed.  The system retains ownership of this list;
+     *               the caller must NOT delete it. Does not include user-registered Calendars.
+     * @stable ICU 2.0
+     */
+    static const Locale* U_EXPORT2 getAvailableLocales(int32_t& count);
+
+
+    /**
+     * Given a key and a locale, returns an array of string values in a preferred
+     * order that would make a difference. These are all and only those values where
+     * the open (creation) of the service with the locale formed from the input locale
+     * plus input keyword and that value has different behavior than creation with the
+     * input locale alone.
+     * @param key           one of the keys supported by this service.  For now, only
+     *                      "calendar" is supported.
+     * @param locale        the locale
+     * @param commonlyUsed  if set to true it will return only commonly used values
+     *                      with the given locale in preferred order.  Otherwise,
+     *                      it will return all the available values for the locale.
+     * @param status        ICU Error Code
+     * @return a string enumeration over keyword values for the given key and the locale.
+     * @stable ICU 4.2
+     */
+    static StringEnumeration* U_EXPORT2 getKeywordValuesForLocale(const char* key,
+                    const Locale& locale, UBool commonlyUsed, UErrorCode& status);
+
+    /**
+     * Returns the current UTC (GMT) time measured in milliseconds since 0:00:00 on 1/1/70
+     * (derived from the system time).
+     *
+     * @return   The current UTC time in milliseconds.
+     * @stable ICU 2.0
+     */
+    static UDate U_EXPORT2 getNow(void);
+
+    /**
+     * Gets this Calendar's time as milliseconds. May involve recalculation of time due
+     * to previous calls to set time field values. The time specified is non-local UTC
+     * (GMT) time. Although this method is const, this object may actually be changed
+     * (semantically const).
+     *
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @return        The current time in UTC (GMT) time, or zero if the operation
+     *                failed.
+     * @stable ICU 2.0
+     */
+    inline UDate getTime(UErrorCode& status) const { return getTimeInMillis(status); }
+
+    /**
+     * Sets this Calendar's current time with the given UDate. The time specified should
+     * be in non-local UTC (GMT) time.
+     *
+     * @param date  The given UDate in UTC (GMT) time.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @stable ICU 2.0
+     */
+    inline void setTime(UDate date, UErrorCode& status) { setTimeInMillis(date, status); }
+
+    /**
+     * Compares the equality of two Calendar objects. Objects of different subclasses
+     * are considered unequal. This comparison is very exacting; two Calendar objects
+     * must be in exactly the same state to be considered equal. To compare based on the
+     * represented time, use equals() instead.
+     *
+     * @param that  The Calendar object to be compared with.
+     * @return      true if the given Calendar is the same as this Calendar; false
+     *              otherwise.
+     * @stable ICU 2.0
+     */
+    virtual bool operator==(const Calendar& that) const;
+
+    /**
+     * Compares the inequality of two Calendar objects.
+     *
+     * @param that  The Calendar object to be compared with.
+     * @return      true if the given Calendar is not the same as this Calendar; false
+     *              otherwise.
+     * @stable ICU 2.0
+     */
+    bool operator!=(const Calendar& that) const {return !operator==(that);}
+
+    /**
+     * Returns true if the given Calendar object is equivalent to this
+     * one.  An equivalent Calendar will behave exactly as this one
+     * does, but it may be set to a different time.  By contrast, for
+     * the operator==() method to return true, the other Calendar must
+     * be set to the same time.
+     *
+     * @param other the Calendar to be compared with this Calendar
+     * @stable ICU 2.4
+     */
+    virtual UBool isEquivalentTo(const Calendar& other) const;
+
+    /**
+     * Compares the Calendar time, whereas Calendar::operator== compares the equality of
+     * Calendar objects.
+     *
+     * @param when    The Calendar to be compared with this Calendar. Although this is a
+     *                const parameter, the object may be modified physically
+     *                (semantically const).
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @return        True if the current time of this Calendar is equal to the time of
+     *                Calendar when; false otherwise.
+     * @stable ICU 2.0
+     */
+    UBool equals(const Calendar& when, UErrorCode& status) const;
+
+    /**
+     * Returns true if this Calendar's current time is before "when"'s current time.
+     *
+     * @param when    The Calendar to be compared with this Calendar. Although this is a
+     *                const parameter, the object may be modified physically
+     *                (semantically const).
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @return        True if the current time of this Calendar is before the time of
+     *                Calendar when; false otherwise.
+     * @stable ICU 2.0
+     */
+    UBool before(const Calendar& when, UErrorCode& status) const;
+
+    /**
+     * Returns true if this Calendar's current time is after "when"'s current time.
+     *
+     * @param when    The Calendar to be compared with this Calendar. Although this is a
+     *                const parameter, the object may be modified physically
+     *                (semantically const).
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @return        True if the current time of this Calendar is after the time of
+     *                Calendar when; false otherwise.
+     * @stable ICU 2.0
+     */
+    UBool after(const Calendar& when, UErrorCode& status) const;
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * UDate Arithmetic function. Adds the specified (signed) amount of time to the given
+     * time field, based on the calendar's rules. For example, to subtract 5 days from
+     * the current time of the calendar, call add(Calendar::DATE, -5). When adding on
+     * the month or Calendar::MONTH field, other fields like date might conflict and
+     * need to be changed. For instance, adding 1 month on the date 01/31/96 will result
+     * in 02/29/96.
+     * Adding a positive value always means moving forward in time, so for the Gregorian calendar,
+     * starting with 100 BC and adding +1 to year results in 99 BC (even though this actually reduces
+     * the numeric value of the field itself).
+     *
+     * @param field   Specifies which date field to modify.
+     * @param amount  The amount of time to be added to the field, in the natural unit
+     *                for that field (e.g., days for the day fields, hours for the hour
+     *                field.)
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @deprecated ICU 2.6. use add(UCalendarDateFields field, int32_t amount, UErrorCode& status) instead.
+     */
+    virtual void add(EDateFields field, int32_t amount, UErrorCode& status);
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /**
+     * UDate Arithmetic function. Adds the specified (signed) amount of time to the given
+     * time field, based on the calendar's rules. For example, to subtract 5 days from
+     * the current time of the calendar, call add(Calendar::DATE, -5). When adding on
+     * the month or Calendar::MONTH field, other fields like date might conflict and
+     * need to be changed. For instance, adding 1 month on the date 01/31/96 will result
+     * in 02/29/96.
+     * Adding a positive value always means moving forward in time, so for the Gregorian calendar,
+     * starting with 100 BC and adding +1 to year results in 99 BC (even though this actually reduces
+     * the numeric value of the field itself).
+     *
+     * @param field   Specifies which date field to modify.
+     * @param amount  The amount of time to be added to the field, in the natural unit
+     *                for that field (e.g., days for the day fields, hours for the hour
+     *                field.)
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @stable ICU 2.6.
+     */
+    virtual void add(UCalendarDateFields field, int32_t amount, UErrorCode& status);
+
+#ifndef U_HIDE_DEPRECATED_API
+    /**
+     * Time Field Rolling function. Rolls (up/down) a single unit of time on the given
+     * time field. For example, to roll the current date up by one day, call
+     * roll(Calendar::DATE, true). When rolling on the year or Calendar::YEAR field, it
+     * will roll the year value in the range between getMinimum(Calendar::YEAR) and the
+     * value returned by getMaximum(Calendar::YEAR). When rolling on the month or
+     * Calendar::MONTH field, other fields like date might conflict and, need to be
+     * changed. For instance, rolling the month up on the date 01/31/96 will result in
+     * 02/29/96. Rolling up always means rolling forward in time (unless the limit of the
+     * field is reached, in which case it may pin or wrap), so for Gregorian calendar,
+     * starting with 100 BC and rolling the year up results in 99 BC.
+     * When eras have a definite beginning and end (as in the Chinese calendar, or as in
+     * most eras in the Japanese calendar) then rolling the year past either limit of the
+     * era will cause the year to wrap around. When eras only have a limit at one end,
+     * then attempting to roll the year past that limit will result in pinning the year
+     * at that limit. Note that for most calendars in which era 0 years move forward in
+     * time (such as Buddhist, Hebrew, or Islamic), it is possible for add or roll to
+     * result in negative years for era 0 (that is the only way to represent years before
+     * the calendar epoch).
+     * When rolling on the hour-in-day or Calendar::HOUR_OF_DAY field, it will roll the
+     * hour value in the range between 0 and 23, which is zero-based.
+     * <P>
+     * NOTE: Do not use this method -- use roll(EDateFields, int, UErrorCode&) instead.
+     *
+     * @param field   The time field.
+     * @param up      Indicates if the value of the specified time field is to be rolled
+     *                up or rolled down. Use true if rolling up, false otherwise.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @deprecated ICU 2.6. Use roll(UCalendarDateFields field, UBool up, UErrorCode& status) instead.
+     */
+    inline void roll(EDateFields field, UBool up, UErrorCode& status);
+#endif  /* U_HIDE_DEPRECATED_API */
+
+    /**
+     * Time Field Rolling function. Rolls (up/down) a single unit of time on the given
+     * time field. For example, to roll the current date up by one day, call
+     * roll(Calendar::DATE, true). When rolling on the year or Calendar::YEAR field, it
+     * will roll the year value in the range between getMinimum(Calendar::YEAR) and the
+     * value returned by getMaximum(Calendar::YEAR). When rolling on the month or
+     * Calendar::MONTH field, other fields like date might conflict and, need to be
+     * changed. For instance, rolling the month up on the date 01/31/96 will result in
+     * 02/29/96. Rolling up always means rolling forward in time (unless the limit of the
+     * field is reached, in which case it may pin or wrap), so for Gregorian calendar,
+     * starting with 100 BC and rolling the year up results in 99 BC.
+     * When eras have a definite beginning and end (as in the Chinese calendar, or as in
+     * most eras in the Japanese calendar) then rolling the year past either limit of the
+     * era will cause the year to wrap around. When eras only have a limit at one end,
+     * then attempting to roll the year past that limit will result in pinning the year
+     * at that limit. Note that for most calendars in which era 0 years move forward in
+     * time (such as Buddhist, Hebrew, or Islamic), it is possible for add or roll to
+     * result in negative years for era 0 (that is the only way to represent years before
+     * the calendar epoch).
+     * When rolling on the hour-in-day or Calendar::HOUR_OF_DAY field, it will roll the
+     * hour value in the range between 0 and 23, which is zero-based.
+     * <P>
+     * NOTE: Do not use this method -- use roll(UCalendarDateFields, int, UErrorCode&) instead.
+     *
+     * @param field   The time field.
+     * @param up      Indicates if the value of the specified time field is to be rolled
+     *                up or rolled down. Use true if rolling up, false otherwise.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @stable ICU 2.6.
+     */
+    inline void roll(UCalendarDateFields field, UBool up, UErrorCode& status);
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * Time Field Rolling function. Rolls by the given amount on the given
+     * time field. For example, to roll the current date up by one day, call
+     * roll(Calendar::DATE, +1, status). When rolling on the month or
+     * Calendar::MONTH field, other fields like date might conflict and, need to be
+     * changed. For instance, rolling the month up on the date 01/31/96 will result in
+     * 02/29/96. Rolling by a positive value always means rolling forward in time (unless
+     * the limit of the field is reached, in which case it may pin or wrap), so for
+     * Gregorian calendar, starting with 100 BC and rolling the year by + 1 results in 99 BC.
+     * When eras have a definite beginning and end (as in the Chinese calendar, or as in
+     * most eras in the Japanese calendar) then rolling the year past either limit of the
+     * era will cause the year to wrap around. When eras only have a limit at one end,
+     * then attempting to roll the year past that limit will result in pinning the year
+     * at that limit. Note that for most calendars in which era 0 years move forward in
+     * time (such as Buddhist, Hebrew, or Islamic), it is possible for add or roll to
+     * result in negative years for era 0 (that is the only way to represent years before
+     * the calendar epoch).
+     * When rolling on the hour-in-day or Calendar::HOUR_OF_DAY field, it will roll the
+     * hour value in the range between 0 and 23, which is zero-based.
+     * <P>
+     * The only difference between roll() and add() is that roll() does not change
+     * the value of more significant fields when it reaches the minimum or maximum
+     * of its range, whereas add() does.
+     *
+     * @param field   The time field.
+     * @param amount  Indicates amount to roll.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid, this will be set to
+     *                an error status.
+     * @deprecated ICU 2.6. Use roll(UCalendarDateFields field, int32_t amount, UErrorCode& status) instead.
+     */
+    virtual void roll(EDateFields field, int32_t amount, UErrorCode& status);
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /**
+     * Time Field Rolling function. Rolls by the given amount on the given
+     * time field. For example, to roll the current date up by one day, call
+     * roll(Calendar::DATE, +1, status). When rolling on the month or
+     * Calendar::MONTH field, other fields like date might conflict and, need to be
+     * changed. For instance, rolling the month up on the date 01/31/96 will result in
+     * 02/29/96. Rolling by a positive value always means rolling forward in time (unless
+     * the limit of the field is reached, in which case it may pin or wrap), so for
+     * Gregorian calendar, starting with 100 BC and rolling the year by + 1 results in 99 BC.
+     * When eras have a definite beginning and end (as in the Chinese calendar, or as in
+     * most eras in the Japanese calendar) then rolling the year past either limit of the
+     * era will cause the year to wrap around. When eras only have a limit at one end,
+     * then attempting to roll the year past that limit will result in pinning the year
+     * at that limit. Note that for most calendars in which era 0 years move forward in
+     * time (such as Buddhist, Hebrew, or Islamic), it is possible for add or roll to
+     * result in negative years for era 0 (that is the only way to represent years before
+     * the calendar epoch).
+     * When rolling on the hour-in-day or Calendar::HOUR_OF_DAY field, it will roll the
+     * hour value in the range between 0 and 23, which is zero-based.
+     * <P>
+     * The only difference between roll() and add() is that roll() does not change
+     * the value of more significant fields when it reaches the minimum or maximum
+     * of its range, whereas add() does.
+     *
+     * @param field   The time field.
+     * @param amount  Indicates amount to roll.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid, this will be set to
+     *                an error status.
+     * @stable ICU 2.6.
+     */
+    virtual void roll(UCalendarDateFields field, int32_t amount, UErrorCode& status);
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * Return the difference between the given time and the time this
+     * calendar object is set to.  If this calendar is set
+     * <em>before</em> the given time, the returned value will be
+     * positive.  If this calendar is set <em>after</em> the given
+     * time, the returned value will be negative.  The
+     * <code>field</code> parameter specifies the units of the return
+     * value.  For example, if <code>fieldDifference(when,
+     * Calendar::MONTH)</code> returns 3, then this calendar is set to
+     * 3 months before <code>when</code>, and possibly some addition
+     * time less than one month.
+     *
+     * <p>As a side effect of this call, this calendar is advanced
+     * toward <code>when</code> by the given amount.  That is, calling
+     * this method has the side effect of calling <code>add(field,
+     * n)</code>, where <code>n</code> is the return value.
+     *
+     * <p>Usage: To use this method, call it first with the largest
+     * field of interest, then with progressively smaller fields.  For
+     * example:
+     *
+     * <pre>
+     * int y = cal->fieldDifference(when, Calendar::YEAR, err);
+     * int m = cal->fieldDifference(when, Calendar::MONTH, err);
+     * int d = cal->fieldDifference(when, Calendar::DATE, err);</pre>
+     *
+     * computes the difference between <code>cal</code> and
+     * <code>when</code> in years, months, and days.
+     *
+     * <p>Note: <code>fieldDifference()</code> is
+     * <em>asymmetrical</em>.  That is, in the following code:
+     *
+     * <pre>
+     * cal->setTime(date1, err);
+     * int m1 = cal->fieldDifference(date2, Calendar::MONTH, err);
+     * int d1 = cal->fieldDifference(date2, Calendar::DATE, err);
+     * cal->setTime(date2, err);
+     * int m2 = cal->fieldDifference(date1, Calendar::MONTH, err);
+     * int d2 = cal->fieldDifference(date1, Calendar::DATE, err);</pre>
+     *
+     * one might expect that <code>m1 == -m2 && d1 == -d2</code>.
+     * However, this is not generally the case, because of
+     * irregularities in the underlying calendar system (e.g., the
+     * Gregorian calendar has a varying number of days per month).
+     *
+     * @param when the date to compare this calendar's time to
+     * @param field the field in which to compute the result
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid, this will be set to
+     *                an error status.
+     * @return the difference, either positive or negative, between
+     * this calendar's time and <code>when</code>, in terms of
+     * <code>field</code>.
+     * @deprecated ICU 2.6. Use fieldDifference(UDate when, UCalendarDateFields field, UErrorCode& status).
+     */
+    virtual int32_t fieldDifference(UDate when, EDateFields field, UErrorCode& status);
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /**
+     * Return the difference between the given time and the time this
+     * calendar object is set to.  If this calendar is set
+     * <em>before</em> the given time, the returned value will be
+     * positive.  If this calendar is set <em>after</em> the given
+     * time, the returned value will be negative.  The
+     * <code>field</code> parameter specifies the units of the return
+     * value.  For example, if <code>fieldDifference(when,
+     * Calendar::MONTH)</code> returns 3, then this calendar is set to
+     * 3 months before <code>when</code>, and possibly some addition
+     * time less than one month.
+     *
+     * <p>As a side effect of this call, this calendar is advanced
+     * toward <code>when</code> by the given amount.  That is, calling
+     * this method has the side effect of calling <code>add(field,
+     * n)</code>, where <code>n</code> is the return value.
+     *
+     * <p>Usage: To use this method, call it first with the largest
+     * field of interest, then with progressively smaller fields.  For
+     * example:
+     *
+     * <pre>
+     * int y = cal->fieldDifference(when, Calendar::YEAR, err);
+     * int m = cal->fieldDifference(when, Calendar::MONTH, err);
+     * int d = cal->fieldDifference(when, Calendar::DATE, err);</pre>
+     *
+     * computes the difference between <code>cal</code> and
+     * <code>when</code> in years, months, and days.
+     *
+     * <p>Note: <code>fieldDifference()</code> is
+     * <em>asymmetrical</em>.  That is, in the following code:
+     *
+     * <pre>
+     * cal->setTime(date1, err);
+     * int m1 = cal->fieldDifference(date2, Calendar::MONTH, err);
+     * int d1 = cal->fieldDifference(date2, Calendar::DATE, err);
+     * cal->setTime(date2, err);
+     * int m2 = cal->fieldDifference(date1, Calendar::MONTH, err);
+     * int d2 = cal->fieldDifference(date1, Calendar::DATE, err);</pre>
+     *
+     * one might expect that <code>m1 == -m2 && d1 == -d2</code>.
+     * However, this is not generally the case, because of
+     * irregularities in the underlying calendar system (e.g., the
+     * Gregorian calendar has a varying number of days per month).
+     *
+     * @param when the date to compare this calendar's time to
+     * @param field the field in which to compute the result
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid, this will be set to
+     *                an error status.
+     * @return the difference, either positive or negative, between
+     * this calendar's time and <code>when</code>, in terms of
+     * <code>field</code>.
+     * @stable ICU 2.6.
+     */
+    virtual int32_t fieldDifference(UDate when, UCalendarDateFields field, UErrorCode& status);
+
+    /**
+     * Sets the calendar's time zone to be the one passed in. The Calendar takes ownership
+     * of the TimeZone; the caller is no longer responsible for deleting it.  If the
+     * given time zone is nullptr, this function has no effect.
+     *
+     * @param value  The given time zone.
+     * @stable ICU 2.0
+     */
+    void adoptTimeZone(TimeZone* value);
+
+    /**
+     * Sets the calendar's time zone to be the same as the one passed in. The TimeZone
+     * passed in is _not_ adopted; the client is still responsible for deleting it.
+     *
+     * @param zone  The given time zone.
+     * @stable ICU 2.0
+     */
+    void setTimeZone(const TimeZone& zone);
+
+    /**
+     * Returns a reference to the time zone owned by this calendar. The returned reference
+     * is only valid until clients make another call to adoptTimeZone or setTimeZone,
+     * or this Calendar is destroyed.
+     *
+     * @return   The time zone object associated with this calendar.
+     * @stable ICU 2.0
+     */
+    const TimeZone& getTimeZone(void) const;
+
+    /**
+     * Returns the time zone owned by this calendar. The caller owns the returned object
+     * and must delete it when done.  After this call, the new time zone associated
+     * with this Calendar is the default TimeZone as returned by TimeZone::createDefault().
+     *
+     * @return   The time zone object which was associated with this calendar.
+     * @stable ICU 2.0
+     */
+    TimeZone* orphanTimeZone(void);
+
+    /**
+     * Queries if the current date for this Calendar is in Daylight Savings Time.
+     *
+     * @param status Fill-in parameter which receives the status of this operation.
+     * @return   True if the current date for this Calendar is in Daylight Savings Time,
+     *           false, otherwise.
+     * @stable ICU 2.0
+     */
+    virtual UBool inDaylightTime(UErrorCode& status) const;
+
+    /**
+     * Specifies whether or not date/time interpretation is to be lenient. With lenient
+     * interpretation, a date such as "February 942, 1996" will be treated as being
+     * equivalent to the 941st day after February 1, 1996. With strict interpretation,
+     * such dates will cause an error when computing time from the time field values
+     * representing the dates.
+     *
+     * @param lenient  True specifies date/time interpretation to be lenient.
+     *
+     * @see            DateFormat#setLenient
+     * @stable ICU 2.0
+     */
+    void setLenient(UBool lenient);
+
+    /**
+     * Tells whether date/time interpretation is to be lenient.
+     *
+     * @return   True tells that date/time interpretation is to be lenient.
+     * @stable ICU 2.0
+     */
+    UBool isLenient(void) const;
+
+    /**
+     * Sets the behavior for handling wall time repeating multiple times
+     * at negative time zone offset transitions. For example, 1:30 AM on
+     * November 6, 2011 in US Eastern time (America/New_York) occurs twice;
+     * 1:30 AM EDT, then 1:30 AM EST one hour later. When <code>UCAL_WALLTIME_FIRST</code>
+     * is used, the wall time 1:30AM in this example will be interpreted as 1:30 AM EDT
+     * (first occurrence). When <code>UCAL_WALLTIME_LAST</code> is used, it will be
+     * interpreted as 1:30 AM EST (last occurrence). The default value is
+     * <code>UCAL_WALLTIME_LAST</code>.
+     * <p>
+     * <b>Note:</b>When <code>UCAL_WALLTIME_NEXT_VALID</code> is not a valid
+     * option for this. When the argument is neither <code>UCAL_WALLTIME_FIRST</code>
+     * nor <code>UCAL_WALLTIME_LAST</code>, this method has no effect and will keep
+     * the current setting.
+     *
+     * @param option the behavior for handling repeating wall time, either
+     * <code>UCAL_WALLTIME_FIRST</code> or <code>UCAL_WALLTIME_LAST</code>.
+     * @see #getRepeatedWallTimeOption
+     * @stable ICU 49
+     */
+    void setRepeatedWallTimeOption(UCalendarWallTimeOption option);
+
+    /**
+     * Gets the behavior for handling wall time repeating multiple times
+     * at negative time zone offset transitions.
+     *
+     * @return the behavior for handling repeating wall time, either
+     * <code>UCAL_WALLTIME_FIRST</code> or <code>UCAL_WALLTIME_LAST</code>.
+     * @see #setRepeatedWallTimeOption
+     * @stable ICU 49
+     */
+    UCalendarWallTimeOption getRepeatedWallTimeOption(void) const;
+
+    /**
+     * Sets the behavior for handling skipped wall time at positive time zone offset
+     * transitions. For example, 2:30 AM on March 13, 2011 in US Eastern time (America/New_York)
+     * does not exist because the wall time jump from 1:59 AM EST to 3:00 AM EDT. When
+     * <code>UCAL_WALLTIME_FIRST</code> is used, 2:30 AM is interpreted as 30 minutes before 3:00 AM
+     * EDT, therefore, it will be resolved as 1:30 AM EST. When <code>UCAL_WALLTIME_LAST</code>
+     * is used, 2:30 AM is interpreted as 31 minutes after 1:59 AM EST, therefore, it will be
+     * resolved as 3:30 AM EDT. When <code>UCAL_WALLTIME_NEXT_VALID</code> is used, 2:30 AM will
+     * be resolved as next valid wall time, that is 3:00 AM EDT. The default value is
+     * <code>UCAL_WALLTIME_LAST</code>.
+     * <p>
+     * <b>Note:</b>This option is effective only when this calendar is lenient.
+     * When the calendar is strict, such non-existing wall time will cause an error.
+     *
+     * @param option the behavior for handling skipped wall time at positive time zone
+     * offset transitions, one of <code>UCAL_WALLTIME_FIRST</code>, <code>UCAL_WALLTIME_LAST</code> and
+     * <code>UCAL_WALLTIME_NEXT_VALID</code>.
+     * @see #getSkippedWallTimeOption
+     *
+     * @stable ICU 49
+     */
+    void setSkippedWallTimeOption(UCalendarWallTimeOption option);
+
+    /**
+     * Gets the behavior for handling skipped wall time at positive time zone offset
+     * transitions.
+     *
+     * @return the behavior for handling skipped wall time, one of
+     * <code>UCAL_WALLTIME_FIRST</code>, <code>UCAL_WALLTIME_LAST</code>
+     * and <code>UCAL_WALLTIME_NEXT_VALID</code>.
+     * @see #setSkippedWallTimeOption
+     * @stable ICU 49
+     */
+    UCalendarWallTimeOption getSkippedWallTimeOption(void) const;
+
+    /**
+     * Sets what the first day of the week is; e.g., Sunday in US, Monday in France.
+     *
+     * @param value  The given first day of the week.
+     * @stable ICU 2.6.
+     */
+    void setFirstDayOfWeek(UCalendarDaysOfWeek value);
+
+#ifndef U_HIDE_DEPRECATED_API
+    /**
+     * Gets what the first day of the week is; e.g., Sunday in US, Monday in France.
+     *
+     * @return   The first day of the week.
+     * @deprecated ICU 2.6 use the overload with error code
+     */
+    EDaysOfWeek getFirstDayOfWeek(void) const;
+#endif  /* U_HIDE_DEPRECATED_API */
+
+    /**
+     * Gets what the first day of the week is; e.g., Sunday in US, Monday in France.
+     *
+     * @param status error code
+     * @return   The first day of the week.
+     * @stable ICU 2.6
+     */
+    UCalendarDaysOfWeek getFirstDayOfWeek(UErrorCode &status) const;
+
+    /**
+     * Sets what the minimal days required in the first week of the year are; For
+     * example, if the first week is defined as one that contains the first day of the
+     * first month of a year, call the method with value 1. If it must be a full week,
+     * use value 7.
+     *
+     * @param value  The given minimal days required in the first week of the year.
+     * @stable ICU 2.0
+     */
+    void setMinimalDaysInFirstWeek(uint8_t value);
+
+    /**
+     * Gets what the minimal days required in the first week of the year are; e.g., if
+     * the first week is defined as one that contains the first day of the first month
+     * of a year, getMinimalDaysInFirstWeek returns 1. If the minimal days required must
+     * be a full week, getMinimalDaysInFirstWeek returns 7.
+     *
+     * @return   The minimal days required in the first week of the year.
+     * @stable ICU 2.0
+     */
+    uint8_t getMinimalDaysInFirstWeek(void) const;
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * Gets the minimum value for the given time field. e.g., for Gregorian
+     * DAY_OF_MONTH, 1.
+     *
+     * @param field  The given time field.
+     * @return       The minimum value for the given time field.
+     * @deprecated ICU 2.6. Use getMinimum(UCalendarDateFields field) instead.
+     */
+    virtual int32_t getMinimum(EDateFields field) const;
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /**
+     * Gets the minimum value for the given time field. e.g., for Gregorian
+     * DAY_OF_MONTH, 1.
+     *
+     * @param field  The given time field.
+     * @return       The minimum value for the given time field.
+     * @stable ICU 2.6.
+     */
+    virtual int32_t getMinimum(UCalendarDateFields field) const;
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * Gets the maximum value for the given time field. e.g. for Gregorian DAY_OF_MONTH,
+     * 31.
+     *
+     * @param field  The given time field.
+     * @return       The maximum value for the given time field.
+     * @deprecated ICU 2.6. Use getMaximum(UCalendarDateFields field) instead.
+     */
+    virtual int32_t getMaximum(EDateFields field) const;
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /**
+     * Gets the maximum value for the given time field. e.g. for Gregorian DAY_OF_MONTH,
+     * 31.
+     *
+     * @param field  The given time field.
+     * @return       The maximum value for the given time field.
+     * @stable ICU 2.6.
+     */
+    virtual int32_t getMaximum(UCalendarDateFields field) const;
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * Gets the highest minimum value for the given field if varies. Otherwise same as
+     * getMinimum(). For Gregorian, no difference.
+     *
+     * @param field  The given time field.
+     * @return       The highest minimum value for the given time field.
+     * @deprecated ICU 2.6. Use getGreatestMinimum(UCalendarDateFields field) instead.
+     */
+    virtual int32_t getGreatestMinimum(EDateFields field) const;
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /**
+     * Gets the highest minimum value for the given field if varies. Otherwise same as
+     * getMinimum(). For Gregorian, no difference.
+     *
+     * @param field  The given time field.
+     * @return       The highest minimum value for the given time field.
+     * @stable ICU 2.6.
+     */
+    virtual int32_t getGreatestMinimum(UCalendarDateFields field) const;
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * Gets the lowest maximum value for the given field if varies. Otherwise same as
+     * getMaximum(). e.g., for Gregorian DAY_OF_MONTH, 28.
+     *
+     * @param field  The given time field.
+     * @return       The lowest maximum value for the given time field.
+     * @deprecated ICU 2.6. Use getLeastMaximum(UCalendarDateFields field) instead.
+     */
+    virtual int32_t getLeastMaximum(EDateFields field) const;
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /**
+     * Gets the lowest maximum value for the given field if varies. Otherwise same as
+     * getMaximum(). e.g., for Gregorian DAY_OF_MONTH, 28.
+     *
+     * @param field  The given time field.
+     * @return       The lowest maximum value for the given time field.
+     * @stable ICU 2.6.
+     */
+    virtual int32_t getLeastMaximum(UCalendarDateFields field) const;
+
+#ifndef U_HIDE_DEPRECATED_API
+    /**
+     * Return the minimum value that this field could have, given the current date.
+     * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
+     *
+     * The version of this function on Calendar uses an iterative algorithm to determine the
+     * actual minimum value for the field.  There is almost always a more efficient way to
+     * accomplish this (in most cases, you can simply return getMinimum()).  GregorianCalendar
+     * overrides this function with a more efficient implementation.
+     *
+     * @param field    the field to determine the minimum of
+     * @param status   Fill-in parameter which receives the status of this operation.
+     * @return         the minimum of the given field for the current date of this Calendar
+     * @deprecated ICU 2.6. Use getActualMinimum(UCalendarDateFields field, UErrorCode& status) instead.
+     */
+    int32_t getActualMinimum(EDateFields field, UErrorCode& status) const;
+#endif  /* U_HIDE_DEPRECATED_API */
+
+    /**
+     * Return the minimum value that this field could have, given the current date.
+     * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
+     *
+     * The version of this function on Calendar uses an iterative algorithm to determine the
+     * actual minimum value for the field.  There is almost always a more efficient way to
+     * accomplish this (in most cases, you can simply return getMinimum()).  GregorianCalendar
+     * overrides this function with a more efficient implementation.
+     *
+     * @param field    the field to determine the minimum of
+     * @param status   Fill-in parameter which receives the status of this operation.
+     * @return         the minimum of the given field for the current date of this Calendar
+     * @stable ICU 2.6.
+     */
+    virtual int32_t getActualMinimum(UCalendarDateFields field, UErrorCode& status) const;
+
+    /**
+     * Return the maximum value that this field could have, given the current date.
+     * For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual
+     * maximum would be 28; for "Feb 3, 1996" it s 29.  Similarly for a Hebrew calendar,
+     * for some years the actual maximum for MONTH is 12, and for others 13.
+     *
+     * The version of this function on Calendar uses an iterative algorithm to determine the
+     * actual maximum value for the field.  There is almost always a more efficient way to
+     * accomplish this (in most cases, you can simply return getMaximum()).  GregorianCalendar
+     * overrides this function with a more efficient implementation.
+     *
+     * @param field    the field to determine the maximum of
+     * @param status   Fill-in parameter which receives the status of this operation.
+     * @return         the maximum of the given field for the current date of this Calendar
+     * @stable ICU 2.6.
+     */
+    virtual int32_t getActualMaximum(UCalendarDateFields field, UErrorCode& status) const;
+
+    /**
+     * Gets the value for a given time field. Recalculate the current time field values
+     * if the time value has been changed by a call to setTime(). Return zero for unset
+     * fields if any fields have been explicitly set by a call to set(). To force a
+     * recomputation of all fields regardless of the previous state, call complete().
+     * This method is semantically const, but may alter the object in memory.
+     *
+     * @param field  The given time field.
+     * @param status Fill-in parameter which receives the status of the operation.
+     * @return       The value for the given time field, or zero if the field is unset,
+     *               and set() has been called for any other field.
+     * @stable ICU 2.6.
+     */
+    int32_t get(UCalendarDateFields field, UErrorCode& status) const;
+
+    /**
+     * Determines if the given time field has a value set. This can affect in the
+     * resolving of time in Calendar. Unset fields have a value of zero, by definition.
+     *
+     * @param field  The given time field.
+     * @return   True if the given time field has a value set; false otherwise.
+     * @stable ICU 2.6.
+     */
+    UBool isSet(UCalendarDateFields field) const;
+
+    /**
+     * Sets the given time field with the given value.
+     *
+     * @param field  The given time field.
+     * @param value  The value to be set for the given time field.
+     * @stable ICU 2.6.
+     */
+    void set(UCalendarDateFields field, int32_t value);
+
+    /**
+     * Sets the values for the fields YEAR, MONTH, and DATE. Other field values are
+     * retained; call clear() first if this is not desired.
+     *
+     * @param year   The value used to set the YEAR time field.
+     * @param month  The value used to set the MONTH time field. Month value is 0-based.
+     *               e.g., 0 for January.
+     * @param date   The value used to set the DATE time field.
+     * @stable ICU 2.0
+     */
+    void set(int32_t year, int32_t month, int32_t date);
+
+    /**
+     * Sets the values for the fields YEAR, MONTH, DATE, HOUR_OF_DAY, and MINUTE. Other
+     * field values are retained; call clear() first if this is not desired.
+     *
+     * @param year    The value used to set the YEAR time field.
+     * @param month   The value used to set the MONTH time field. Month value is
+     *                0-based. E.g., 0 for January.
+     * @param date    The value used to set the DATE time field.
+     * @param hour    The value used to set the HOUR_OF_DAY time field.
+     * @param minute  The value used to set the MINUTE time field.
+     * @stable ICU 2.0
+     */
+    void set(int32_t year, int32_t month, int32_t date, int32_t hour, int32_t minute);
+
+    /**
+     * Sets the values for the fields YEAR, MONTH, DATE, HOUR_OF_DAY, MINUTE, and SECOND.
+     * Other field values are retained; call clear() first if this is not desired.
+     *
+     * @param year    The value used to set the YEAR time field.
+     * @param month   The value used to set the MONTH time field. Month value is
+     *                0-based. E.g., 0 for January.
+     * @param date    The value used to set the DATE time field.
+     * @param hour    The value used to set the HOUR_OF_DAY time field.
+     * @param minute  The value used to set the MINUTE time field.
+     * @param second  The value used to set the SECOND time field.
+     * @stable ICU 2.0
+     */
+    void set(int32_t year, int32_t month, int32_t date, int32_t hour, int32_t minute, int32_t second);
+
+    /**
+     * Clears the values of all the time fields, making them both unset and assigning
+     * them a value of zero. The field values will be determined during the next
+     * resolving of time into time fields.
+     * @stable ICU 2.0
+     */
+    void clear(void);
+
+    /**
+     * Clears the value in the given time field, both making it unset and assigning it a
+     * value of zero. This field value will be determined during the next resolving of
+     * time into time fields.
+     *
+     * @param field  The time field to be cleared.
+     * @stable ICU 2.6.
+     */
+    void clear(UCalendarDateFields field);
+
+    /**
+     * Returns a unique class ID POLYMORPHICALLY. Pure virtual method. This method is to
+     * implement a simple version of RTTI, since not all C++ compilers support genuine
+     * RTTI. Polymorphic operator==() and clone() methods call this method.
+     * <P>
+     * Concrete subclasses of Calendar must implement getDynamicClassID() and also a
+     * static method and data member:
+     *
+     *      static UClassID getStaticClassID() { return (UClassID)&amp;fgClassID; }
+     *      static char fgClassID;
+     *
+     * @return   The class ID for this object. All objects of a given class have the
+     *           same class ID. Objects of other classes have different class IDs.
+     * @stable ICU 2.0
+     */
+    virtual UClassID getDynamicClassID(void) const override = 0;
+
+    /**
+     * Returns the calendar type name string for this Calendar object.
+     * The returned string is the legacy ICU calendar attribute value,
+     * for example, "gregorian" or "japanese".
+     *
+     * See type="old type name" for the calendar attribute of locale IDs
+     * at http://www.unicode.org/reports/tr35/#Key_Type_Definitions
+     *
+     * Sample code for getting the LDML/BCP 47 calendar key value:
+     * \code
+     * const char *calType = cal->getType();
+     * if (0 == strcmp(calType, "unknown")) {
+     *     // deal with unknown calendar type
+     * } else {
+     *     string localeID("root@calendar=");
+     *     localeID.append(calType);
+     *     char langTag[100];
+     *     UErrorCode errorCode = U_ZERO_ERROR;
+     *     int32_t length = uloc_toLanguageTag(localeID.c_str(), langTag, (int32_t)sizeof(langTag), true, &errorCode);
+     *     if (U_FAILURE(errorCode)) {
+     *         // deal with errors & overflow
+     *     }
+     *     string lang(langTag, length);
+     *     size_t caPos = lang.find("-ca-");
+     *     lang.erase(0, caPos + 4);
+     *     // lang now contains the LDML calendar type
+     * }
+     * \endcode
+     *
+     * @return legacy calendar type name string
+     * @stable ICU 49
+     */
+    virtual const char * getType() const = 0;
+
+    /**
+     * Returns whether the given day of the week is a weekday, a weekend day,
+     * or a day that transitions from one to the other, for the locale and
+     * calendar system associated with this Calendar (the locale's region is
+     * often the most determinant factor). If a transition occurs at midnight,
+     * then the days before and after the transition will have the
+     * type UCAL_WEEKDAY or UCAL_WEEKEND. If a transition occurs at a time
+     * other than midnight, then the day of the transition will have
+     * the type UCAL_WEEKEND_ONSET or UCAL_WEEKEND_CEASE. In this case, the
+     * method getWeekendTransition() will return the point of
+     * transition.
+     * @param dayOfWeek The day of the week whose type is desired (UCAL_SUNDAY..UCAL_SATURDAY).
+     * @param status The error code for the operation.
+     * @return The UCalendarWeekdayType for the day of the week.
+     * @stable ICU 4.4
+     */
+    virtual UCalendarWeekdayType getDayOfWeekType(UCalendarDaysOfWeek dayOfWeek, UErrorCode &status) const;
+
+    /**
+     * Returns the time during the day at which the weekend begins or ends in
+     * this calendar system.  If getDayOfWeekType() returns UCAL_WEEKEND_ONSET
+     * for the specified dayOfWeek, return the time at which the weekend begins.
+     * If getDayOfWeekType() returns UCAL_WEEKEND_CEASE for the specified dayOfWeek,
+     * return the time at which the weekend ends. If getDayOfWeekType() returns
+     * some other UCalendarWeekdayType for the specified dayOfWeek, is it an error condition
+     * (U_ILLEGAL_ARGUMENT_ERROR).
+     * @param dayOfWeek The day of the week for which the weekend transition time is
+     * desired (UCAL_SUNDAY..UCAL_SATURDAY).
+     * @param status The error code for the operation.
+     * @return The milliseconds after midnight at which the weekend begins or ends.
+     * @stable ICU 4.4
+     */
+    virtual int32_t getWeekendTransition(UCalendarDaysOfWeek dayOfWeek, UErrorCode &status) const;
+
+    /**
+     * Returns true if the given UDate is in the weekend in
+     * this calendar system.
+     * @param date The UDate in question.
+     * @param status The error code for the operation.
+     * @return true if the given UDate is in the weekend in
+     * this calendar system, false otherwise.
+     * @stable ICU 4.4
+     */
+    virtual UBool isWeekend(UDate date, UErrorCode &status) const;
+
+    /**
+     * Returns true if this Calendar's current date-time is in the weekend in
+     * this calendar system.
+     * @return true if this Calendar's current date-time is in the weekend in
+     * this calendar system, false otherwise.
+     * @stable ICU 4.4
+     */
+    virtual UBool isWeekend(void) const;
+
+#ifndef U_FORCE_HIDE_DRAFT_API
+    /**
+     * Returns true if the date is in a leap year. Recalculate the current time
+     * field values if the time value has been changed by a call to * setTime().
+     * This method is semantically const, but may alter the object in memory.
+     * A "leap year" is a year that contains more days than other years (for
+     * solar or lunar calendars) or more months than other years (for lunisolar
+     * calendars like Hebrew or Chinese), as defined in the ECMAScript Temporal
+     * proposal.
+     *
+     * @param status        ICU Error Code
+     * @return       True if the date in the fields is in a Temporal proposal
+     *               defined leap year. False otherwise.
+     * @draft ICU 73
+     */
+    virtual bool inTemporalLeapYear(UErrorCode& status) const;
+
+    /**
+     * Gets The Temporal monthCode value corresponding to the month for the date.
+     * The value is a string identifier that starts with the literal grapheme
+     * "M" followed by two graphemes representing the zero-padded month number
+     * of the current month in a normal (non-leap) year and suffixed by an
+     * optional literal grapheme "L" if this is a leap month in a lunisolar
+     * calendar. The 25 possible values are "M01" .. "M13" and "M01L" .. "M12L".
+     * For the Hebrew calendar, the values are "M01" .. "M12" for non-leap year, and
+     * "M01" .. "M05", "M05L", "M06" .. "M12" for leap year.
+     * For the Chinese calendar, the values are "M01" .. "M12" for non-leap year and
+     * in leap year with another monthCode in "M01L" .. "M12L".
+     * For Coptic and Ethiopian calendar, the Temporal monthCode values for any
+     * years are "M01" to "M13".
+     *
+     * @param status        ICU Error Code
+     * @return       One of 25 possible strings in {"M01".."M13", "M01L".."M12L"}.
+     * @draft ICU 73
+     */
+    virtual const char* getTemporalMonthCode(UErrorCode& status) const;
+
+    /**
+     * Sets The Temporal monthCode which is a string identifier that starts
+     * with the literal grapheme "M" followed by two graphemes representing
+     * the zero-padded month number of the current month in a normal
+     * (non-leap) year and suffixed by an optional literal grapheme "L" if this
+     * is a leap month in a lunisolar calendar. The 25 possible values are
+     * "M01" .. "M13" and "M01L" .. "M12L". For Hebrew calendar, the values are
+     * "M01" .. "M12" for non-leap years, and "M01" .. "M05", "M05L", "M06"
+     * .. "M12" for leap year.
+     * For the Chinese calendar, the values are "M01" .. "M12" for non-leap year and
+     * in leap year with another monthCode in "M01L" .. "M12L".
+     * For Coptic and Ethiopian calendar, the Temporal monthCode values for any
+     * years are "M01" to "M13".
+     *
+     * @param temporalMonth  The value to be set for temporal monthCode.
+     * @param status        ICU Error Code
+     *
+     * @draft ICU 73
+     */
+    virtual void setTemporalMonthCode(const char* temporalMonth, UErrorCode& status);
+
+#endif  // U_FORCE_HIDE_DRAFT_API
+
+protected:
+
+     /**
+      * Constructs a Calendar with the default time zone as returned by
+      * TimeZone::createInstance(), and the default locale.
+      *
+      * @param success  Indicates the status of Calendar object construction. Returns
+      *                 U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+      */
+    Calendar(UErrorCode& success);
+
+    /**
+     * Copy constructor
+     *
+     * @param source    Calendar object to be copied from
+     * @stable ICU 2.0
+     */
+    Calendar(const Calendar& source);
+
+    /**
+     * Default assignment operator
+     *
+     * @param right    Calendar object to be copied
+     * @stable ICU 2.0
+     */
+    Calendar& operator=(const Calendar& right);
+
+    /**
+     * Constructs a Calendar with the given time zone and locale. Clients are no longer
+     * responsible for deleting the given time zone object after it's adopted.
+     *
+     * @param zone     The given time zone.
+     * @param aLocale  The given locale.
+     * @param success  Indicates the status of Calendar object construction. Returns
+     *                 U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    Calendar(TimeZone* zone, const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Constructs a Calendar with the given time zone and locale.
+     *
+     * @param zone     The given time zone.
+     * @param aLocale  The given locale.
+     * @param success  Indicates the status of Calendar object construction. Returns
+     *                 U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    Calendar(const TimeZone& zone, const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Converts Calendar's time field values to GMT as milliseconds.
+     *
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @stable ICU 2.0
+     */
+    virtual void computeTime(UErrorCode& status);
+
+    /**
+     * Converts GMT as milliseconds to time field values. This allows you to sync up the
+     * time field values with a new time that is set for the calendar.  This method
+     * does NOT recompute the time first; to recompute the time, then the fields, use
+     * the method complete().
+     *
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @stable ICU 2.0
+     */
+    virtual void computeFields(UErrorCode& status);
+
+    /**
+     * Gets this Calendar's current time as a long.
+     *
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @return the current time as UTC milliseconds from the epoch.
+     * @stable ICU 2.0
+     */
+    double getTimeInMillis(UErrorCode& status) const;
+
+    /**
+     * Sets this Calendar's current time from the given long value.
+     * @param millis  the new time in UTC milliseconds from the epoch.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @stable ICU 2.0
+     */
+    void setTimeInMillis( double millis, UErrorCode& status );
+
+    /**
+     * Recomputes the current time from currently set fields, and then fills in any
+     * unset fields in the time field list.
+     *
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     * @stable ICU 2.0
+     */
+    void complete(UErrorCode& status);
+
+#ifndef U_HIDE_DEPRECATED_API
+    /**
+     * Gets the value for a given time field. Subclasses can use this function to get
+     * field values without forcing recomputation of time.
+     *
+     * @param field  The given time field.
+     * @return       The value for the given time field.
+     * @deprecated ICU 2.6. Use internalGet(UCalendarDateFields field) instead.
+     */
+    inline int32_t internalGet(EDateFields field) const {return fFields[field];}
+#endif  /* U_HIDE_DEPRECATED_API */
+
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Gets the value for a given time field. Subclasses can use this function to get
+     * field values without forcing recomputation of time. If the field's stamp is UNSET,
+     * the defaultValue is used.
+     *
+     * @param field  The given time field.
+     * @param defaultValue a default value used if the field is unset.
+     * @return       The value for the given time field.
+     * @internal
+     */
+    inline int32_t internalGet(UCalendarDateFields field, int32_t defaultValue) const {return fStamp[field]>kUnset ? fFields[field] : defaultValue;}
+
+    /**
+     * Gets the value for a given time field. Subclasses can use this function to get
+     * field values without forcing recomputation of time.
+     *
+     * @param field  The given time field.
+     * @return       The value for the given time field.
+     * @internal
+     */
+    inline int32_t internalGet(UCalendarDateFields field) const {return fFields[field];}
+#endif  /* U_HIDE_INTERNAL_API */
+
+    /**
+     * Use this function instead of internalGet(UCAL_MONTH). The implementation
+     * check the timestamp of UCAL_MONTH and UCAL_ORDINAL_MONTH and use the
+     * one set later. The subclass should override it to conver the value of UCAL_ORDINAL_MONTH
+     * to UCAL_MONTH correctly if UCAL_ORDINAL_MONTH has higher priority.
+     *
+     * @return       The value for the UCAL_MONTH.
+     * @internal
+     */
+    virtual int32_t internalGetMonth() const;
+
+    /**
+     * Use this function instead of internalGet(UCAL_MONTH, defaultValue). The implementation
+     * check the timestamp of UCAL_MONTH and UCAL_ORDINAL_MONTH and use the
+     * one set later. The subclass should override it to conver the value of UCAL_ORDINAL_MONTH
+     * to UCAL_MONTH correctly if UCAL_ORDINAL_MONTH has higher priority.
+     *
+     * @param defaultValue a default value used if the UCAL_MONTH and
+     *   UCAL_ORDINAL are both unset.
+     * @return       The value for the UCAL_MONTH.
+     * @internal
+     */
+    virtual int32_t internalGetMonth(int32_t defaultValue) const;
+
+#ifndef U_HIDE_DEPRECATED_API
+    /**
+     * Sets the value for a given time field.  This is a fast internal method for
+     * subclasses.  It does not affect the areFieldsInSync, isTimeSet, or areAllFieldsSet
+     * flags.
+     *
+     * @param field    The given time field.
+     * @param value    The value for the given time field.
+     * @deprecated ICU 2.6. Use internalSet(UCalendarDateFields field, int32_t value) instead.
+     */
+    void internalSet(EDateFields field, int32_t value);
+#endif  /* U_HIDE_DEPRECATED_API */
+
+    /**
+     * Sets the value for a given time field.  This is a fast internal method for
+     * subclasses.  It does not affect the areFieldsInSync, isTimeSet, or areAllFieldsSet
+     * flags.
+     *
+     * @param field    The given time field.
+     * @param value    The value for the given time field.
+     * @stable ICU 2.6.
+     */
+    inline void internalSet(UCalendarDateFields field, int32_t value);
+
+    /**
+     * Prepare this calendar for computing the actual minimum or maximum.
+     * This method modifies this calendar's fields; it is called on a
+     * temporary calendar.
+     * @internal
+     */
+    virtual void prepareGetActual(UCalendarDateFields field, UBool isMinimum, UErrorCode &status);
+
+    /**
+     * Limit enums. Not in sync with UCalendarLimitType (refers to internal fields).
+     * @internal
+     */
+    enum ELimitType {
+#ifndef U_HIDE_INTERNAL_API
+      UCAL_LIMIT_MINIMUM = 0,
+      UCAL_LIMIT_GREATEST_MINIMUM,
+      UCAL_LIMIT_LEAST_MAXIMUM,
+      UCAL_LIMIT_MAXIMUM,
+      UCAL_LIMIT_COUNT
+#endif  /* U_HIDE_INTERNAL_API */
+    };
+
+    /**
+     * Subclass API for defining limits of different types.
+     * Subclasses must implement this method to return limits for the
+     * following fields:
+     *
+     * <pre>UCAL_ERA
+     * UCAL_YEAR
+     * UCAL_MONTH
+     * UCAL_WEEK_OF_YEAR
+     * UCAL_WEEK_OF_MONTH
+     * UCAL_DATE (DAY_OF_MONTH on Java)
+     * UCAL_DAY_OF_YEAR
+     * UCAL_DAY_OF_WEEK_IN_MONTH
+     * UCAL_YEAR_WOY
+     * UCAL_EXTENDED_YEAR</pre>
+     *
+     * @param field one of the above field numbers
+     * @param limitType one of <code>MINIMUM</code>, <code>GREATEST_MINIMUM</code>,
+     * <code>LEAST_MAXIMUM</code>, or <code>MAXIMUM</code>
+     * @internal
+     */
+    virtual int32_t handleGetLimit(UCalendarDateFields field, ELimitType limitType) const = 0;
+
+    /**
+     * Return a limit for a field.
+     * @param field the field, from <code>0..UCAL_MAX_FIELD</code>
+     * @param limitType the type specifier for the limit
+     * @see #ELimitType
+     * @internal
+     */
+    virtual int32_t getLimit(UCalendarDateFields field, ELimitType limitType) const;
+
+    /**
+     * Return the Julian day number of day before the first day of the
+     * given month in the given extended year.  Subclasses should override
+     * this method to implement their calendar system.
+     * @param eyear the extended year
+     * @param month the zero-based month, or 0 if useMonth is false
+     * @param useMonth if false, compute the day before the first day of
+     * the given year, otherwise, compute the day before the first day of
+     * the given month
+     * @return the Julian day number of the day before the first
+     * day of the given month and year
+     * @internal
+     */
+    virtual int32_t handleComputeMonthStart(int32_t eyear, int32_t month,
+                                                   UBool useMonth) const  = 0;
+
+    /**
+     * Return the number of days in the given month of the given extended
+     * year of this calendar system.  Subclasses should override this
+     * method if they can provide a more correct or more efficient
+     * implementation than the default implementation in Calendar.
+     * @internal
+     */
+    virtual int32_t handleGetMonthLength(int32_t extendedYear, int32_t month) const ;
+
+    /**
+     * Return the number of days in the given extended year of this
+     * calendar system.  Subclasses should override this method if they can
+     * provide a more correct or more efficient implementation than the
+     * default implementation in Calendar.
+     * @stable ICU 2.0
+     */
+    virtual int32_t handleGetYearLength(int32_t eyear) const;
+
+
+    /**
+     * Return the extended year defined by the current fields.  This will
+     * use the UCAL_EXTENDED_YEAR field or the UCAL_YEAR and supra-year fields (such
+     * as UCAL_ERA) specific to the calendar system, depending on which set of
+     * fields is newer.
+     * @return the extended year
+     * @internal
+     */
+    virtual int32_t handleGetExtendedYear() = 0;
+
+    /**
+     * Subclasses may override this.  This method calls
+     * handleGetMonthLength() to obtain the calendar-specific month
+     * length.
+     * @param bestField which field to use to calculate the date
+     * @return julian day specified by calendar fields.
+     * @internal
+     */
+    virtual int32_t handleComputeJulianDay(UCalendarDateFields bestField);
+
+    /**
+     * Subclasses must override this to convert from week fields
+     * (YEAR_WOY and WEEK_OF_YEAR) to an extended year in the case
+     * where YEAR, EXTENDED_YEAR are not set.
+     * The Calendar implementation assumes yearWoy is in extended gregorian form
+     * @return the extended year, UCAL_EXTENDED_YEAR
+     * @internal
+     */
+    virtual int32_t handleGetExtendedYearFromWeekFields(int32_t yearWoy, int32_t woy);
+
+    /**
+     * Validate a single field of this calendar.  Subclasses should
+     * override this method to validate any calendar-specific fields.
+     * Generic fields can be handled by `Calendar::validateField()`.
+     * @internal
+     */
+    virtual void validateField(UCalendarDateFields field, UErrorCode &status);
+
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Compute the Julian day from fields.  Will determine whether to use
+     * the JULIAN_DAY field directly, or other fields.
+     * @return the julian day
+     * @internal
+     */
+    int32_t computeJulianDay();
+
+    /**
+     * Compute the milliseconds in the day from the fields.  This is a
+     * value from 0 to 23:59:59.999 inclusive, unless fields are out of
+     * range, in which case it can be an arbitrary value.  This value
+     * reflects local zone wall time.
+     * @internal
+     */
+    double computeMillisInDay();
+
+    /**
+     * This method can assume EXTENDED_YEAR has been set.
+     * @param millis milliseconds of the date fields
+     * @param millisInDay milliseconds of the time fields; may be out
+     * or range.
+     * @param ec Output param set to failure code on function return
+     *          when this function fails.
+     * @internal
+     */
+    int32_t computeZoneOffset(double millis, double millisInDay, UErrorCode &ec);
+
+
+    /**
+     * Determine the best stamp in a range.
+     * @param start first enum to look at
+     * @param end last enum to look at
+     * @param bestSoFar stamp prior to function call
+     * @return the stamp value of the best stamp
+     * @internal
+     */
+    int32_t newestStamp(UCalendarDateFields start, UCalendarDateFields end, int32_t bestSoFar) const;
+
+    /**
+     * Marker for end of resolve set (row or group). Value for field resolution tables.
+     *
+     * @see #resolveFields
+     * @internal
+     */
+    static constexpr int32_t kResolveSTOP = -1;
+    /**
+     * Value to be bitwised "ORed" against resolve table field values for remapping.
+     * Example: (UCAL_DATE | kResolveRemap) in 1st column will cause 'UCAL_DATE' to be returned,
+     * but will not examine the value of UCAL_DATE.
+     * Value for field resolution tables.
+     *
+     * @see #resolveFields
+     * @internal
+     */
+    static constexpr int32_t kResolveRemap = 32;
+
+    /**
+     * Precedence table for Dates
+     * @see #resolveFields
+     * @internal
+     */
+    static const UFieldResolutionTable kDatePrecedence[];
+
+    /**
+     * Precedence table for Year
+     * @see #resolveFields
+     * @internal
+     */
+    static const UFieldResolutionTable kYearPrecedence[];
+
+    /**
+     * Precedence table for Day of Week
+     * @see #resolveFields
+     * @internal
+     */
+    static const UFieldResolutionTable kDOWPrecedence[];
+
+    /**
+     * Precedence table for Months
+     * @see #resolveFields
+     * @internal
+     */
+    static const UFieldResolutionTable kMonthPrecedence[];
+
+    /**
+     * Given a precedence table, return the newest field combination in
+     * the table, or UCAL_FIELD_COUNT if none is found.
+     *
+     * <p>The precedence table is a 3-dimensional array of integers.  It
+     * may be thought of as an array of groups.  Each group is an array of
+     * lines.  Each line is an array of field numbers.  Within a line, if
+     * all fields are set, then the time stamp of the line is taken to be
+     * the stamp of the most recently set field.  If any field of a line is
+     * unset, then the line fails to match.  Within a group, the line with
+     * the newest time stamp is selected.  The first field of the line is
+     * returned to indicate which line matched.
+     *
+     * <p>In some cases, it may be desirable to map a line to field that
+     * whose stamp is NOT examined.  For example, if the best field is
+     * DAY_OF_WEEK then the DAY_OF_WEEK_IN_MONTH algorithm may be used.  In
+     * order to do this, insert the value <code>kResolveRemap | F</code> at
+     * the start of the line, where <code>F</code> is the desired return
+     * field value.  This field will NOT be examined; it only determines
+     * the return value if the other fields in the line are the newest.
+     *
+     * <p>If all lines of a group contain at least one unset field, then no
+     * line will match, and the group as a whole will fail to match.  In
+     * that case, the next group will be processed.  If all groups fail to
+     * match, then UCAL_FIELD_COUNT is returned.
+     * @internal
+     */
+    UCalendarDateFields resolveFields(const UFieldResolutionTable *precedenceTable) const;
+#endif  /* U_HIDE_INTERNAL_API */
+
+
+    /**
+     * @internal
+     */
+    virtual const UFieldResolutionTable* getFieldResolutionTable() const;
+
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Return the field that is newer, either defaultField, or
+     * alternateField.  If neither is newer or neither is set, return defaultField.
+     * @internal
+     */
+    UCalendarDateFields newerField(UCalendarDateFields defaultField, UCalendarDateFields alternateField) const;
+#endif  /* U_HIDE_INTERNAL_API */
+
+
+private:
+    /**
+     * Helper function for calculating limits by trial and error
+     * @param field The field being investigated
+     * @param startValue starting (least max) value of field
+     * @param endValue ending (greatest max) value of field
+     * @param status return type
+     * @internal (private)
+     */
+    int32_t getActualHelper(UCalendarDateFields field, int32_t startValue, int32_t endValue, UErrorCode &status) const;
+
+
+protected:
+    /**
+     * The flag which indicates if the current time is set in the calendar.
+     * @stable ICU 2.0
+     */
+    UBool      fIsTimeSet;
+
+    /**
+     * True if the fields are in sync with the currently set time of this Calendar.
+     * If false, then the next attempt to get the value of a field will
+     * force a recomputation of all fields from the current value of the time
+     * field.
+     * <P>
+     * This should really be named areFieldsInSync, but the old name is retained
+     * for backward compatibility.
+     * @stable ICU 2.0
+     */
+    UBool      fAreFieldsSet;
+
+    /**
+     * True if all of the fields have been set.  This is initially false, and set to
+     * true by computeFields().
+     * @stable ICU 2.0
+     */
+    UBool      fAreAllFieldsSet;
+
+    /**
+     * True if all fields have been virtually set, but have not yet been
+     * computed.  This occurs only in setTimeInMillis().  A calendar set
+     * to this state will compute all fields from the time if it becomes
+     * necessary, but otherwise will delay such computation.
+     * @stable ICU 3.0
+     */
+    UBool fAreFieldsVirtuallySet;
+
+    /**
+     * Get the current time without recomputing.
+     *
+     * @return     the current time without recomputing.
+     * @stable ICU 2.0
+     */
+    UDate        internalGetTime(void) const     { return fTime; }
+
+    /**
+     * Set the current time without affecting flags or fields.
+     *
+     * @param time    The time to be set
+     * @return        the current time without recomputing.
+     * @stable ICU 2.0
+     */
+    void        internalSetTime(UDate time)     { fTime = time; }
+
+    /**
+     * The time fields containing values into which the millis is computed.
+     * @stable ICU 2.0
+     */
+    int32_t     fFields[UCAL_FIELD_COUNT];
+
+#ifndef U_FORCE_HIDE_DEPRECATED_API
+    /**
+     * The flags which tell if a specified time field for the calendar is set.
+     * @deprecated ICU 2.8 use (fStamp[n]!=kUnset)
+     */
+    UBool      fIsSet[UCAL_FIELD_COUNT];
+#endif  // U_FORCE_HIDE_DEPRECATED_API
+
+    /** Special values of stamp[]
+     * @stable ICU 2.0
+     */
+    enum {
+        kUnset                 = 0,
+        kInternallySet,
+        kMinimumUserStamp
+    };
+
+    /**
+     * Pseudo-time-stamps which specify when each field was set. There
+     * are two special values, UNSET and INTERNALLY_SET. Values from
+     * MINIMUM_USER_SET to Integer.MAX_VALUE are legal user set values.
+     * @stable ICU 2.0
+     */
+    int32_t        fStamp[UCAL_FIELD_COUNT];
+
+    /**
+     * Subclasses may override this method to compute several fields
+     * specific to each calendar system.  These are:
+     *
+     * <ul><li>ERA
+     * <li>YEAR
+     * <li>MONTH
+     * <li>DAY_OF_MONTH
+     * <li>DAY_OF_YEAR
+     * <li>EXTENDED_YEAR</ul>
+     *
+     * Subclasses can refer to the DAY_OF_WEEK and DOW_LOCAL fields, which
+     * will be set when this method is called.  Subclasses can also call
+     * the getGregorianXxx() methods to obtain Gregorian calendar
+     * equivalents for the given Julian day.
+     *
+     * <p>In addition, subclasses should compute any subclass-specific
+     * fields, that is, fields from BASE_FIELD_COUNT to
+     * getFieldCount() - 1.
+     *
+     * <p>The default implementation in <code>Calendar</code> implements
+     * a pure proleptic Gregorian calendar.
+     * @internal
+     */
+    virtual void handleComputeFields(int32_t julianDay, UErrorCode &status);
+
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Return the extended year on the Gregorian calendar as computed by
+     * <code>computeGregorianFields()</code>.
+     * @internal
+     */
+    int32_t getGregorianYear() const {
+        return fGregorianYear;
+    }
+
+    /**
+     * Return the month (0-based) on the Gregorian calendar as computed by
+     * <code>computeGregorianFields()</code>.
+     * @internal
+     */
+    int32_t getGregorianMonth() const {
+        return fGregorianMonth;
+    }
+
+    /**
+     * Return the day of year (1-based) on the Gregorian calendar as
+     * computed by <code>computeGregorianFields()</code>.
+     * @internal
+     */
+    int32_t getGregorianDayOfYear() const {
+        return fGregorianDayOfYear;
+    }
+
+    /**
+     * Return the day of month (1-based) on the Gregorian calendar as
+     * computed by <code>computeGregorianFields()</code>.
+     * @internal
+     */
+    int32_t getGregorianDayOfMonth() const {
+      return fGregorianDayOfMonth;
+    }
+#endif  /* U_HIDE_INTERNAL_API */
+
+    /**
+     * Called by computeJulianDay.  Returns the default month (0-based) for the year,
+     * taking year and era into account.  Defaults to 0 for Gregorian, which doesn't care.
+     * @param eyear The extended year
+     * @internal
+     */
+    virtual int32_t getDefaultMonthInYear(int32_t eyear) ;
+
+
+    /**
+     * Called by computeJulianDay.  Returns the default day (1-based) for the month,
+     * taking currently-set year and era into account.  Defaults to 1 for Gregorian.
+     * @param eyear the extended year
+     * @param month the month in the year
+     * @internal
+     */
+    virtual int32_t getDefaultDayInMonth(int32_t eyear, int32_t month);
+
+    //-------------------------------------------------------------------------
+    // Protected utility methods for use by subclasses.  These are very handy
+    // for implementing add, roll, and computeFields.
+    //-------------------------------------------------------------------------
+
+    /**
+     * Adjust the specified field so that it is within
+     * the allowable range for the date to which this calendar is set.
+     * For example, in a Gregorian calendar pinning the {@link #UCalendarDateFields DAY_OF_MONTH}
+     * field for a calendar set to April 31 would cause it to be set
+     * to April 30.
+     * <p>
+     * <b>Subclassing:</b>
+     * <br>
+     * This utility method is intended for use by subclasses that need to implement
+     * their own overrides of {@link #roll roll} and {@link #add add}.
+     * <p>
+     * <b>Note:</b>
+     * <code>pinField</code> is implemented in terms of
+     * {@link #getActualMinimum getActualMinimum}
+     * and {@link #getActualMaximum getActualMaximum}.  If either of those methods uses
+     * a slow, iterative algorithm for a particular field, it would be
+     * unwise to attempt to call <code>pinField</code> for that field.  If you
+     * really do need to do so, you should override this method to do
+     * something more efficient for that field.
+     * <p>
+     * @param field The calendar field whose value should be pinned.
+     * @param status Output param set to failure code on function return
+     *          when this function fails.
+     *
+     * @see #getActualMinimum
+     * @see #getActualMaximum
+     * @stable ICU 2.0
+     */
+    virtual void pinField(UCalendarDateFields field, UErrorCode& status);
+
+    /**
+     * Return the week number of a day, within a period. This may be the week number in
+     * a year or the week number in a month. Usually this will be a value >= 1, but if
+     * some initial days of the period are excluded from week 1, because
+     * {@link #getMinimalDaysInFirstWeek getMinimalDaysInFirstWeek} is > 1, then
+     * the week number will be zero for those
+     * initial days. This method requires the day number and day of week for some
+     * known date in the period in order to determine the day of week
+     * on the desired day.
+     * <p>
+     * <b>Subclassing:</b>
+     * <br>
+     * This method is intended for use by subclasses in implementing their
+     * {@link #computeTime computeTime} and/or {@link #computeFields computeFields} methods.
+     * It is often useful in {@link #getActualMinimum getActualMinimum} and
+     * {@link #getActualMaximum getActualMaximum} as well.
+     * <p>
+     * This variant is handy for computing the week number of some other
+     * day of a period (often the first or last day of the period) when its day
+     * of the week is not known but the day number and day of week for some other
+     * day in the period (e.g. the current date) <em>is</em> known.
+     * <p>
+     * @param desiredDay    The {@link #UCalendarDateFields DAY_OF_YEAR} or
+     *              {@link #UCalendarDateFields DAY_OF_MONTH} whose week number is desired.
+     *              Should be 1 for the first day of the period.
+     *
+     * @param dayOfPeriod   The {@link #UCalendarDateFields DAY_OF_YEAR}
+     *              or {@link #UCalendarDateFields DAY_OF_MONTH} for a day in the period whose
+     *              {@link #UCalendarDateFields DAY_OF_WEEK} is specified by the
+     *              <code>knownDayOfWeek</code> parameter.
+     *              Should be 1 for first day of period.
+     *
+     * @param dayOfWeek  The {@link #UCalendarDateFields DAY_OF_WEEK} for the day
+     *              corresponding to the <code>knownDayOfPeriod</code> parameter.
+     *              1-based with 1=Sunday.
+     *
+     * @return      The week number (one-based), or zero if the day falls before
+     *              the first week because
+     *              {@link #getMinimalDaysInFirstWeek getMinimalDaysInFirstWeek}
+     *              is more than one.
+     *
+     * @stable ICU 2.8
+     */
+    int32_t weekNumber(int32_t desiredDay, int32_t dayOfPeriod, int32_t dayOfWeek);
+
+
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Return the week number of a day, within a period. This may be the week number in
+     * a year, or the week number in a month. Usually this will be a value >= 1, but if
+     * some initial days of the period are excluded from week 1, because
+     * {@link #getMinimalDaysInFirstWeek getMinimalDaysInFirstWeek} is > 1,
+     * then the week number will be zero for those
+     * initial days. This method requires the day of week for the given date in order to
+     * determine the result.
+     * <p>
+     * <b>Subclassing:</b>
+     * <br>
+     * This method is intended for use by subclasses in implementing their
+     * {@link #computeTime computeTime} and/or {@link #computeFields computeFields} methods.
+     * It is often useful in {@link #getActualMinimum getActualMinimum} and
+     * {@link #getActualMaximum getActualMaximum} as well.
+     * <p>
+     * @param dayOfPeriod   The {@link #UCalendarDateFields DAY_OF_YEAR} or
+     *                      {@link #UCalendarDateFields DAY_OF_MONTH} whose week number is desired.
+     *                      Should be 1 for the first day of the period.
+     *
+     * @param dayOfWeek     The {@link #UCalendarDateFields DAY_OF_WEEK} for the day
+     *                      corresponding to the <code>dayOfPeriod</code> parameter.
+     *                      1-based with 1=Sunday.
+     *
+     * @return      The week number (one-based), or zero if the day falls before
+     *              the first week because
+     *              {@link #getMinimalDaysInFirstWeek getMinimalDaysInFirstWeek}
+     *              is more than one.
+     * @internal
+     */
+    inline int32_t weekNumber(int32_t dayOfPeriod, int32_t dayOfWeek);
+
+    /**
+     * returns the local DOW, valid range 0..6
+     * @internal
+     */
+    int32_t getLocalDOW();
+#endif  /* U_HIDE_INTERNAL_API */
+
+private:
+
+    /**
+     * The next available value for fStamp[]
+     */
+    int32_t fNextStamp;// = MINIMUM_USER_STAMP;
+
+    /**
+     * Recalculates the time stamp array (fStamp).
+     * Resets fNextStamp to lowest next stamp value.
+     */
+    void recalculateStamp();
+
+    /**
+     * The current time set for the calendar.
+     */
+    UDate        fTime;
+
+    /**
+     * @see   #setLenient
+     */
+    UBool      fLenient;
+
+    /**
+     * Time zone affects the time calculation done by Calendar. Calendar subclasses use
+     * the time zone data to produce the local time. Always set; never nullptr.
+     */
+    TimeZone*   fZone;
+
+    /**
+     * Option for repeated wall time
+     * @see #setRepeatedWallTimeOption
+     */
+    UCalendarWallTimeOption fRepeatedWallTime;
+
+    /**
+     * Option for skipped wall time
+     * @see #setSkippedWallTimeOption
+     */
+    UCalendarWallTimeOption fSkippedWallTime;
+
+    /**
+     * Both firstDayOfWeek and minimalDaysInFirstWeek are locale-dependent. They are
+     * used to figure out the week count for a specific date for a given locale. These
+     * must be set when a Calendar is constructed. For example, in US locale,
+     * firstDayOfWeek is SUNDAY; minimalDaysInFirstWeek is 1. They are used to figure
+     * out the week count for a specific date for a given locale. These must be set when
+     * a Calendar is constructed.
+     */
+    UCalendarDaysOfWeek fFirstDayOfWeek;
+    uint8_t     fMinimalDaysInFirstWeek;
+    UCalendarDaysOfWeek fWeekendOnset;
+    int32_t fWeekendOnsetMillis;
+    UCalendarDaysOfWeek fWeekendCease;
+    int32_t fWeekendCeaseMillis;
+
+    /**
+     * Sets firstDayOfWeek and minimalDaysInFirstWeek. Called at Calendar construction
+     * time.
+     *
+     * @param desiredLocale  The given locale.
+     * @param type           The calendar type identifier, e.g: gregorian, buddhist, etc.
+     * @param success        Indicates the status of setting the week count data from
+     *                       the resource for the given locale. Returns U_ZERO_ERROR if
+     *                       constructed successfully.
+     */
+    void        setWeekData(const Locale& desiredLocale, const char *type, UErrorCode& success);
+
+    /**
+     * Recompute the time and update the status fields isTimeSet
+     * and areFieldsSet.  Callers should check isTimeSet and only
+     * call this method if isTimeSet is false.
+     *
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid or restricted by
+     *                leniency, this will be set to an error status.
+     */
+    void updateTime(UErrorCode& status);
+
+    /**
+     * The Gregorian year, as computed by computeGregorianFields() and
+     * returned by getGregorianYear().
+     * @see #computeGregorianFields
+     */
+    int32_t fGregorianYear;
+
+    /**
+     * The Gregorian month, as computed by computeGregorianFields() and
+     * returned by getGregorianMonth().
+     * @see #computeGregorianFields
+     */
+    int32_t fGregorianMonth;
+
+    /**
+     * The Gregorian day of the year, as computed by
+     * computeGregorianFields() and returned by getGregorianDayOfYear().
+     * @see #computeGregorianFields
+     */
+    int32_t fGregorianDayOfYear;
+
+    /**
+     * The Gregorian day of the month, as computed by
+     * computeGregorianFields() and returned by getGregorianDayOfMonth().
+     * @see #computeGregorianFields
+     */
+    int32_t fGregorianDayOfMonth;
+
+    /* calculations */
+
+    /**
+     * Compute the Gregorian calendar year, month, and day of month from
+     * the given Julian day.  These values are not stored in fields, but in
+     * member variables gregorianXxx.  Also compute the DAY_OF_WEEK and
+     * DOW_LOCAL fields.
+     */
+    void computeGregorianAndDOWFields(int32_t julianDay, UErrorCode &ec);
+
+protected:
+
+    /**
+     * Compute the Gregorian calendar year, month, and day of month from the
+     * Julian day.  These values are not stored in fields, but in member
+     * variables gregorianXxx.  They are used for time zone computations and by
+     * subclasses that are Gregorian derivatives.  Subclasses may call this
+     * method to perform a Gregorian calendar millis->fields computation.
+     */
+    void computeGregorianFields(int32_t julianDay, UErrorCode &ec);
+
+private:
+
+    /**
+     * Compute the fields WEEK_OF_YEAR, YEAR_WOY, WEEK_OF_MONTH,
+     * DAY_OF_WEEK_IN_MONTH, and DOW_LOCAL from EXTENDED_YEAR, YEAR,
+     * DAY_OF_WEEK, and DAY_OF_YEAR.  The latter fields are computed by the
+     * subclass based on the calendar system.
+     *
+     * <p>The YEAR_WOY field is computed simplistically.  It is equal to YEAR
+     * most of the time, but at the year boundary it may be adjusted to YEAR-1
+     * or YEAR+1 to reflect the overlap of a week into an adjacent year.  In
+     * this case, a simple increment or decrement is performed on YEAR, even
+     * though this may yield an invalid YEAR value.  For instance, if the YEAR
+     * is part of a calendar system with an N-year cycle field CYCLE, then
+     * incrementing the YEAR may involve incrementing CYCLE and setting YEAR
+     * back to 0 or 1.  This is not handled by this code, and in fact cannot be
+     * simply handled without having subclasses define an entire parallel set of
+     * fields for fields larger than or equal to a year.  This additional
+     * complexity is not warranted, since the intention of the YEAR_WOY field is
+     * to support ISO 8601 notation, so it will typically be used with a
+     * proleptic Gregorian calendar, which has no field larger than a year.
+     */
+    void computeWeekFields(UErrorCode &ec);
+
+
+    /**
+     * Ensure that each field is within its valid range by calling {@link
+     * #validateField(int, int&)} on each field that has been set.  This method
+     * should only be called if this calendar is not lenient.
+     * @see #isLenient
+     * @see #validateField(int, int&)
+     */
+    void validateFields(UErrorCode &status);
+
+    /**
+     * Validate a single field of this calendar given its minimum and
+     * maximum allowed value.  If the field is out of range,
+     * <code>U_ILLEGAL_ARGUMENT_ERROR</code> will be set.  Subclasses may
+     * use this method in their implementation of {@link
+     * #validateField(int, int&)}.
+     */
+    void validateField(UCalendarDateFields field, int32_t min, int32_t max, UErrorCode& status);
+
+ protected:
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Convert a quasi Julian date to the day of the week. The Julian date used here is
+     * not a true Julian date, since it is measured from midnight, not noon. Return
+     * value is one-based.
+     *
+     * @param julian  The given Julian date number.
+     * @return   Day number from 1..7 (SUN..SAT).
+     * @internal
+     */
+    static uint8_t julianDayToDayOfWeek(double julian);
+#endif  /* U_HIDE_INTERNAL_API */
+
+ private:
+    char validLocale[ULOC_FULLNAME_CAPACITY];
+    char actualLocale[ULOC_FULLNAME_CAPACITY];
+
+ public:
+#if !UCONFIG_NO_SERVICE
+    /**
+     * INTERNAL FOR 2.6 --  Registration.
+     */
+
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Return a StringEnumeration over the locales available at the time of the call,
+     * including registered locales.
+     * @return a StringEnumeration over the locales available at the time of the call
+     * @internal
+     */
+    static StringEnumeration* getAvailableLocales(void);
+
+    /**
+     * Register a new Calendar factory.  The factory will be adopted.
+     * INTERNAL in 2.6
+     *
+     * Because ICU may choose to cache Calendars internally, this must
+     * be called at application startup, prior to any calls to
+     * Calendar::createInstance to avoid undefined behavior.
+     *
+     * @param toAdopt the factory instance to be adopted
+     * @param status the in/out status code, no special meanings are assigned
+     * @return a registry key that can be used to unregister this factory
+     * @internal
+     */
+    static URegistryKey registerFactory(ICUServiceFactory* toAdopt, UErrorCode& status);
+
+    /**
+     * Unregister a previously-registered CalendarFactory using the key returned from the
+     * register call.  Key becomes invalid after a successful call and should not be used again.
+     * The CalendarFactory corresponding to the key will be deleted.
+     * INTERNAL in 2.6
+     *
+     * Because ICU may choose to cache Calendars internally, this should
+     * be called during application shutdown, after all calls to
+     * Calendar::createInstance to avoid undefined behavior.
+     *
+     * @param key the registry key returned by a previous call to registerFactory
+     * @param status the in/out status code, no special meanings are assigned
+     * @return true if the factory for the key was successfully unregistered
+     * @internal
+     */
+    static UBool unregister(URegistryKey key, UErrorCode& status);
+#endif  /* U_HIDE_INTERNAL_API */
+
+    /**
+     * Multiple Calendar Implementation
+     * @internal
+     */
+    friend class CalendarFactory;
+
+    /**
+     * Multiple Calendar Implementation
+     * @internal
+     */
+    friend class CalendarService;
+
+    /**
+     * Multiple Calendar Implementation
+     * @internal
+     */
+    friend class DefaultCalendarFactory;
+#endif /* !UCONFIG_NO_SERVICE */
+
+    /**
+     * @return true if this calendar has a default century (i.e. 03 -> 2003)
+     * @internal
+     */
+    virtual UBool haveDefaultCentury() const = 0;
+
+    /**
+     * @return the start of the default century, as a UDate
+     * @internal
+     */
+    virtual UDate defaultCenturyStart() const = 0;
+    /**
+     * @return the beginning year of the default century, as a year
+     * @internal
+     */
+    virtual int32_t defaultCenturyStartYear() const = 0;
+
+    /** Get the locale for this calendar object. You can choose between valid and actual locale.
+     *  @param type type of the locale we're looking for (valid or actual)
+     *  @param status error code for the operation
+     *  @return the locale
+     *  @stable ICU 2.8
+     */
+    Locale getLocale(ULocDataLocaleType type, UErrorCode &status) const;
+
+    /**
+     * @return      The related Gregorian year; will be obtained by modifying the value
+     *              obtained by get from UCAL_EXTENDED_YEAR field
+     * @internal
+     */
+    virtual int32_t getRelatedYear(UErrorCode &status) const;
+
+    /**
+     * @param year  The related Gregorian year to set; will be modified as necessary then
+     *              set in UCAL_EXTENDED_YEAR field
+     * @internal
+     */
+    virtual void setRelatedYear(int32_t year);
+
+#ifndef U_HIDE_INTERNAL_API
+    /** Get the locale for this calendar object. You can choose between valid and actual locale.
+     *  @param type type of the locale we're looking for (valid or actual)
+     *  @param status error code for the operation
+     *  @return the locale
+     *  @internal
+     */
+    const char* getLocaleID(ULocDataLocaleType type, UErrorCode &status) const;
+#endif  /* U_HIDE_INTERNAL_API */
+
+private:
+    /**
+     * Cast TimeZone used by this object to BasicTimeZone, or nullptr if the TimeZone
+     * is not an instance of BasicTimeZone.
+     */
+    BasicTimeZone* getBasicTimeZone() const;
+
+    /**
+     * Find the previous zone transition near the given time.
+     * @param base The base time, inclusive
+     * @param transitionTime Receives the result time
+     * @param status The error status
+     * @return true if a transition is found.
+     */
+    UBool getImmediatePreviousZoneTransition(UDate base, UDate *transitionTime, UErrorCode& status) const;
+
+public:
+#ifndef U_HIDE_INTERNAL_API
+    /**
+     * Creates a new Calendar from a Locale for the cache.
+     * This method does not set the time or timezone in returned calendar.
+     * @param locale the locale.
+     * @param status any error returned here.
+     * @return the new Calendar object with no time or timezone set.
+     * @internal For ICU use only.
+     */
+    static Calendar * U_EXPORT2 makeInstance(
+            const Locale &locale, UErrorCode &status);
+
+    /**
+     * Get the calendar type for given locale.
+     * @param locale the locale
+     * @param typeBuffer calendar type returned here
+     * @param typeBufferSize The size of typeBuffer in bytes. If the type
+     *   can't fit in the buffer, this method sets status to
+     *   U_BUFFER_OVERFLOW_ERROR
+     * @param status error, if any, returned here.
+     * @internal For ICU use only.
+     */
+    static void U_EXPORT2 getCalendarTypeFromLocale(
+            const Locale &locale,
+            char *typeBuffer,
+            int32_t typeBufferSize,
+            UErrorCode &status);
+#endif  /* U_HIDE_INTERNAL_API */
+};
+
+// -------------------------------------
+
+inline Calendar*
+Calendar::createInstance(TimeZone* zone, UErrorCode& errorCode)
+{
+    // since the Locale isn't specified, use the default locale
+    return createInstance(zone, Locale::getDefault(), errorCode);
+}
+
+// -------------------------------------
+
+inline void
+Calendar::roll(UCalendarDateFields field, UBool up, UErrorCode& status)
+{
+    roll(field, (int32_t)(up ? +1 : -1), status);
+}
+
+#ifndef U_HIDE_DEPRECATED_API
+inline void
+Calendar::roll(EDateFields field, UBool up, UErrorCode& status)
+{
+    roll((UCalendarDateFields) field, up, status);
+}
+#endif  /* U_HIDE_DEPRECATED_API */
+
+
+// -------------------------------------
+
+/**
+ * Fast method for subclasses.  The caller must maintain fUserSetDSTOffset and
+ * fUserSetZoneOffset, as well as the isSet[] array.
+ */
+
+inline void
+Calendar::internalSet(UCalendarDateFields field, int32_t value)
+{
+    fFields[field] = value;
+    fStamp[field] = kInternallySet;
+    fIsSet[field]     = true; // Remove later
+}
+
+
+#ifndef U_HIDE_INTERNAL_API
+inline int32_t  Calendar::weekNumber(int32_t dayOfPeriod, int32_t dayOfWeek)
+{
+  return weekNumber(dayOfPeriod, dayOfPeriod, dayOfWeek);
+}
+#endif  /* U_HIDE_INTERNAL_API */
+
+U_NAMESPACE_END
+
+#endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* U_SHOW_CPLUSPLUS_API */
+
+#endif // _CALENDAR