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diff --git a/src/include/utils/datetime.h b/src/include/utils/datetime.h
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+/*-------------------------------------------------------------------------
+ *
+ * datetime.h
+ *	  Definitions for date/time support code.
+ *	  The support code is shared with other date data types,
+ *	   including date, and time.
+ *
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/datetime.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef DATETIME_H
+#define DATETIME_H
+
+#include "nodes/nodes.h"
+#include "utils/timestamp.h"
+
+/* this struct is declared in utils/tzparser.h: */
+struct tzEntry;
+
+
+/* ----------------------------------------------------------------
+ *				time types + support macros
+ *
+ * String definitions for standard time quantities.
+ *
+ * These strings are the defaults used to form output time strings.
+ * Other alternative forms are hardcoded into token tables in datetime.c.
+ * ----------------------------------------------------------------
+ */
+
+#define DAGO			"ago"
+#define DCURRENT		"current"
+#define EPOCH			"epoch"
+#define INVALID			"invalid"
+#define EARLY			"-infinity"
+#define LATE			"infinity"
+#define NOW				"now"
+#define TODAY			"today"
+#define TOMORROW		"tomorrow"
+#define YESTERDAY		"yesterday"
+#define ZULU			"zulu"
+
+#define DMICROSEC		"usecond"
+#define DMILLISEC		"msecond"
+#define DSECOND			"second"
+#define DMINUTE			"minute"
+#define DHOUR			"hour"
+#define DDAY			"day"
+#define DWEEK			"week"
+#define DMONTH			"month"
+#define DQUARTER		"quarter"
+#define DYEAR			"year"
+#define DDECADE			"decade"
+#define DCENTURY		"century"
+#define DMILLENNIUM		"millennium"
+#define DA_D			"ad"
+#define DB_C			"bc"
+#define DTIMEZONE		"timezone"
+
+/*
+ * Fundamental time field definitions for parsing.
+ *
+ *	Meridian:  am, pm, or 24-hour style.
+ *	Millennium: ad, bc
+ */
+
+#define AM		0
+#define PM		1
+#define HR24	2
+
+#define AD		0
+#define BC		1
+
+/*
+ * Field types for time decoding.
+ *
+ * Can't have more of these than there are bits in an unsigned int
+ * since these are turned into bit masks during parsing and decoding.
+ *
+ * Furthermore, the values for YEAR, MONTH, DAY, HOUR, MINUTE, SECOND
+ * must be in the range 0..14 so that the associated bitmasks can fit
+ * into the left half of an INTERVAL's typmod value.  Since those bits
+ * are stored in typmods, you can't change them without initdb!
+ */
+
+#define RESERV	0
+#define MONTH	1
+#define YEAR	2
+#define DAY		3
+#define JULIAN	4
+#define TZ		5				/* fixed-offset timezone abbreviation */
+#define DTZ		6				/* fixed-offset timezone abbrev, DST */
+#define DYNTZ	7				/* dynamic timezone abbreviation */
+#define IGNORE_DTF	8
+#define AMPM	9
+#define HOUR	10
+#define MINUTE	11
+#define SECOND	12
+#define MILLISECOND 13
+#define MICROSECOND 14
+#define DOY		15
+#define DOW		16
+#define UNITS	17
+#define ADBC	18
+/* these are only for relative dates */
+#define AGO		19
+#define ABS_BEFORE		20
+#define ABS_AFTER		21
+/* generic fields to help with parsing */
+#define ISODATE 22
+#define ISOTIME 23
+/* these are only for parsing intervals */
+#define WEEK		24
+#define DECADE		25
+#define CENTURY		26
+#define MILLENNIUM	27
+/* hack for parsing two-word timezone specs "MET DST" etc */
+#define DTZMOD	28				/* "DST" as a separate word */
+/* reserved for unrecognized string values */
+#define UNKNOWN_FIELD	31
+
+/*
+ * Token field definitions for time parsing and decoding.
+ *
+ * Some field type codes (see above) use these as the "value" in datetktbl[].
+ * These are also used for bit masks in DecodeDateTime and friends
+ *	so actually restrict them to within [0,31] for now.
+ * - thomas 97/06/19
+ * Not all of these fields are used for masks in DecodeDateTime
+ *	so allow some larger than 31. - thomas 1997-11-17
+ *
+ * Caution: there are undocumented assumptions in the code that most of these
+ * values are not equal to IGNORE_DTF nor RESERV.  Be very careful when
+ * renumbering values in either of these apparently-independent lists :-(
+ */
+
+#define DTK_NUMBER		0
+#define DTK_STRING		1
+
+#define DTK_DATE		2
+#define DTK_TIME		3
+#define DTK_TZ			4
+#define DTK_AGO			5
+
+#define DTK_SPECIAL		6
+#define DTK_EARLY		9
+#define DTK_LATE		10
+#define DTK_EPOCH		11
+#define DTK_NOW			12
+#define DTK_YESTERDAY	13
+#define DTK_TODAY		14
+#define DTK_TOMORROW	15
+#define DTK_ZULU		16
+
+#define DTK_DELTA		17
+#define DTK_SECOND		18
+#define DTK_MINUTE		19
+#define DTK_HOUR		20
+#define DTK_DAY			21
+#define DTK_WEEK		22
+#define DTK_MONTH		23
+#define DTK_QUARTER		24
+#define DTK_YEAR		25
+#define DTK_DECADE		26
+#define DTK_CENTURY		27
+#define DTK_MILLENNIUM	28
+#define DTK_MILLISEC	29
+#define DTK_MICROSEC	30
+#define DTK_JULIAN		31
+
+#define DTK_DOW			32
+#define DTK_DOY			33
+#define DTK_TZ_HOUR		34
+#define DTK_TZ_MINUTE	35
+#define DTK_ISOYEAR		36
+#define DTK_ISODOW		37
+
+
+/*
+ * Bit mask definitions for time parsing.
+ */
+
+#define DTK_M(t)		(0x01 << (t))
+
+/* Convenience: a second, plus any fractional component */
+#define DTK_ALL_SECS_M	(DTK_M(SECOND) | DTK_M(MILLISECOND) | DTK_M(MICROSECOND))
+#define DTK_DATE_M		(DTK_M(YEAR) | DTK_M(MONTH) | DTK_M(DAY))
+#define DTK_TIME_M		(DTK_M(HOUR) | DTK_M(MINUTE) | DTK_ALL_SECS_M)
+
+/*
+ * Working buffer size for input and output of interval, timestamp, etc.
+ * Inputs that need more working space will be rejected early.  Longer outputs
+ * will overrun buffers, so this must suffice for all possible output.  As of
+ * this writing, interval_out() needs the most space at ~90 bytes.
+ */
+#define MAXDATELEN		128
+/* maximum possible number of fields in a date string */
+#define MAXDATEFIELDS	25
+/* only this many chars are stored in datetktbl */
+#define TOKMAXLEN		10
+
+/* keep this struct small; it gets used a lot */
+typedef struct
+{
+	char		token[TOKMAXLEN + 1];	/* always NUL-terminated */
+	char		type;			/* see field type codes above */
+	int32		value;			/* meaning depends on type */
+} datetkn;
+
+/* one of its uses is in tables of time zone abbreviations */
+typedef struct TimeZoneAbbrevTable
+{
+	Size		tblsize;		/* size in bytes of TimeZoneAbbrevTable */
+	int			numabbrevs;		/* number of entries in abbrevs[] array */
+	datetkn		abbrevs[FLEXIBLE_ARRAY_MEMBER];
+	/* DynamicZoneAbbrev(s) may follow the abbrevs[] array */
+} TimeZoneAbbrevTable;
+
+/* auxiliary data for a dynamic time zone abbreviation (non-fixed-offset) */
+typedef struct DynamicZoneAbbrev
+{
+	pg_tz	   *tz;				/* NULL if not yet looked up */
+	char		zone[FLEXIBLE_ARRAY_MEMBER];	/* NUL-terminated zone name */
+} DynamicZoneAbbrev;
+
+
+/* FMODULO()
+ * Macro to replace modf(), which is broken on some platforms.
+ * t = input and remainder
+ * q = integer part
+ * u = divisor
+ */
+#define FMODULO(t,q,u) \
+do { \
+	(q) = (((t) < 0) ? ceil((t) / (u)) : floor((t) / (u))); \
+	if ((q) != 0) (t) -= rint((q) * (u)); \
+} while(0)
+
+/* TMODULO()
+ * Like FMODULO(), but work on the timestamp datatype (now always int64).
+ * We assume that int64 follows the C99 semantics for division (negative
+ * quotients truncate towards zero).
+ */
+#define TMODULO(t,q,u) \
+do { \
+	(q) = ((t) / (u)); \
+	if ((q) != 0) (t) -= ((q) * (u)); \
+} while(0)
+
+/*
+ * Date/time validation
+ * Include check for leap year.
+ */
+
+extern PGDLLIMPORT const char *const months[];	/* months (3-char
+												 * abbreviations) */
+extern PGDLLIMPORT const char *const days[];	/* days (full names) */
+extern PGDLLIMPORT const int day_tab[2][13];
+
+/*
+ * These are the rules for the Gregorian calendar, which was adopted in 1582.
+ * However, we use this calculation for all prior years as well because the
+ * SQL standard specifies use of the Gregorian calendar.  This prevents the
+ * date 1500-02-29 from being stored, even though it is valid in the Julian
+ * calendar.
+ */
+#define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
+
+
+/*
+ * Datetime input parsing routines (ParseDateTime, DecodeDateTime, etc)
+ * return zero or a positive value on success.  On failure, they return
+ * one of these negative code values.  DateTimeParseError may be used to
+ * produce a correct ereport.
+ */
+#define DTERR_BAD_FORMAT		(-1)
+#define DTERR_FIELD_OVERFLOW	(-2)
+#define DTERR_MD_FIELD_OVERFLOW (-3)	/* triggers hint about DateStyle */
+#define DTERR_INTERVAL_OVERFLOW (-4)
+#define DTERR_TZDISP_OVERFLOW	(-5)
+
+
+extern void GetCurrentDateTime(struct pg_tm *tm);
+extern void GetCurrentTimeUsec(struct pg_tm *tm, fsec_t *fsec, int *tzp);
+extern void j2date(int jd, int *year, int *month, int *day);
+extern int	date2j(int year, int month, int day);
+
+extern int	ParseDateTime(const char *timestr, char *workbuf, size_t buflen,
+						  char **field, int *ftype,
+						  int maxfields, int *numfields);
+extern int	DecodeDateTime(char **field, int *ftype,
+						   int nf, int *dtype,
+						   struct pg_tm *tm, fsec_t *fsec, int *tzp);
+extern int	DecodeTimezone(char *str, int *tzp);
+extern int	DecodeTimeOnly(char **field, int *ftype,
+						   int nf, int *dtype,
+						   struct pg_tm *tm, fsec_t *fsec, int *tzp);
+extern int	DecodeInterval(char **field, int *ftype, int nf, int range,
+						   int *dtype, struct pg_itm_in *itm_in);
+extern int	DecodeISO8601Interval(char *str,
+								  int *dtype, struct pg_itm_in *itm_in);
+
+extern void DateTimeParseError(int dterr, const char *str,
+							   const char *datatype) pg_attribute_noreturn();
+
+extern int	DetermineTimeZoneOffset(struct pg_tm *tm, pg_tz *tzp);
+extern int	DetermineTimeZoneAbbrevOffset(struct pg_tm *tm, const char *abbr, pg_tz *tzp);
+extern int	DetermineTimeZoneAbbrevOffsetTS(TimestampTz ts, const char *abbr,
+											pg_tz *tzp, int *isdst);
+
+extern void EncodeDateOnly(struct pg_tm *tm, int style, char *str);
+extern void EncodeTimeOnly(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, int style, char *str);
+extern void EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char *tzn, int style, char *str);
+extern void EncodeInterval(struct pg_itm *itm, int style, char *str);
+extern void EncodeSpecialTimestamp(Timestamp dt, char *str);
+
+extern int	ValidateDate(int fmask, bool isjulian, bool is2digits, bool bc,
+						 struct pg_tm *tm);
+
+extern int	DecodeTimezoneAbbrev(int field, char *lowtoken,
+								 int *offset, pg_tz **tz);
+extern int	DecodeSpecial(int field, char *lowtoken, int *val);
+extern int	DecodeUnits(int field, char *lowtoken, int *val);
+
+extern int	j2day(int jd);
+
+extern Node *TemporalSimplify(int32 max_precis, Node *node);
+
+extern bool CheckDateTokenTables(void);
+
+extern TimeZoneAbbrevTable *ConvertTimeZoneAbbrevs(struct tzEntry *abbrevs,
+												   int n);
+extern void InstallTimeZoneAbbrevs(TimeZoneAbbrevTable *tbl);
+
+extern void AdjustTimestampForTypmod(Timestamp *time, int32 typmod);
+extern bool AdjustTimestampForTypmodError(Timestamp *time, int32 typmod,
+										  bool *error);
+
+#endif							/* DATETIME_H */