B.1. Date/Time Input Interpretation

B.1. Date/Time Input Interpretation
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+ Date/time input strings are decoded using the following procedure. +

+ Break the input string into tokens and categorize each token as + a string, time, time zone, or number. +
1. + If the numeric token contains a colon (:), this is + a time string. Include all subsequent digits and colons. +
2. + If the numeric token contains a dash (-), slash + (/), or two or more dots (.), this is + a date string which might have a text month. If a date token has + already been seen, it is instead interpreted as a time zone + name (e.g., America/New_York). +
3. + If the token is numeric only, then it is either a single field + or an ISO 8601 concatenated date (e.g., + 19990113 for January 13, 1999) or time + (e.g., 141516 for 14:15:16). +
4. + If the token starts with a plus (+) or minus + (-), then it is either a numeric time zone or a special + field. +
+ If the token is an alphabetic string, match up with possible strings: +
1. + See if the token matches any known time zone abbreviation. + These abbreviations are supplied by the configuration file + described in Section B.4. +
2. + If not found, search an internal table to match + the token as either a special string (e.g., today), + day (e.g., Thursday), + month (e.g., January), + or noise word (e.g., at, on). +
3. + If still not found, throw an error. +
+ When the token is a number or number field: +
1. + If there are eight or six digits, + and if no other date fields have been previously read, then interpret + as a “concatenated date” (e.g., + 19990118 or 990118). + The interpretation is YYYYMMDD or YYMMDD. +
2. + If the token is three digits + and a year has already been read, then interpret as day of year. +
3. + If four or six digits and a year has already been read, then + interpret as a time (HHMM or HHMMSS). +
4. + If three or more digits and no date fields have yet been found, + interpret as a year (this forces yy-mm-dd ordering of the remaining + date fields). +
5. + Otherwise the date field ordering is assumed to follow the + DateStyle setting: mm-dd-yy, dd-mm-yy, or yy-mm-dd. + Throw an error if a month or day field is found to be out of range. +
+ If BC has been specified, negate the year and add one for + internal storage. (There is no year zero in the Gregorian + calendar, so numerically 1 BC becomes year zero.) +
+ If BC was not specified, and if the year field was two digits in length, + then adjust the year to four digits. If the field is less than 70, then + add 2000, otherwise add 1900. + +
Tip
+ Gregorian years AD 1–99 can be entered by using 4 digits with leading + zeros (e.g., 0099 is AD 99). +
+