| Description | Format | Examples |
|---|---|---|
| daysuf | "st" | "nd" | "rd" | "th" | |
| dd | ([0-2]?[0-9] | "3"[01]) daysuf? | "7th", "22nd", "31" |
| DD | "0" [0-9] | [1-2][0-9] | "3" [01] | "07", "31" |
| m | 'january' | 'february' | 'march' | 'april' | 'may' | 'june' | 'july' | 'august' | 'september' | 'october' | 'november' | 'december' | 'jan' | 'feb' | 'mar' | 'apr' | 'may' | 'jun' | 'jul' | 'aug' | 'sep' | 'sept' | 'oct' | 'nov' | 'dec' | "I" | "II" | "III" | "IV" | "V" | "VI" | "VII" | "VIII" | "IX" | "X" | "XI" | "XII" | |
| M | 'jan' | 'feb' | 'mar' | 'apr' | 'may' | 'jun' | 'jul' | 'aug' | 'sep' | 'sept' | 'oct' | 'nov' | 'dec' | |
| mm | "0"? [0-9] | "1"[0-2] | "0", "04", "7", "12" |
| MM | "0" [0-9] | "1"[0-2] | "00", "04", "07", "12" |
| y | [0-9]{1,4} | "00", "78", "08", "8", "2008" |
| yy | [0-9]{2} | "00", "08", "78" |
| YY | [0-9]{4} | "2000", "2008", "1978" |
| Description | Format | Examples |
|---|---|---|
| American month and day | mm "/" dd | "5/12", "10/27" |
| American month, day and year | mm "/" dd "/" y | "12/22/78", "1/17/2006", "1/17/6" |
| Four digit year, month and day with slashes | YY "/" mm "/" dd | "2008/6/30", "1978/12/22" |
| Four digit year and month (GNU) | YY "-" mm | "2008-6", "2008-06", "1978-12" |
| Year, month and day with dashes | y "-" mm "-" dd | "2008-6-30", "78-12-22", "8-6-21" |
| Day, month and four digit year, with dots, tabs or dashes | dd [.\t-] mm [.-] YY | "30-6-2008", "22.12\t1978" |
| Day, month and two digit year, with dots or tabs | dd [.\t] mm "." yy | "30.6.08", "22\t12\t78" |
| Day, textual month and year | dd ([ \t.-])* m ([ \t.-])* y | "30-June 2008", "22DEC78", "14 III 1879" |
| Textual month and four digit year (Day reset to 1) | m ([ \t.-])* YY | "June 2008", "DEC1978", "March 1879" |
| Four digit year and textual month (Day reset to 1) | YY ([ \t.-])* m | "2008 June", "1978-XII", "1879.MArCH" |
| Textual month, day and year | m ([ .\t-])* dd [,.stndrh\t ]+ y | "July 1st, 2008", "April 17, 1790", "May.9,78" |
| Textual month and day | m ([ .\t-])* dd [,.stndrh\t ]* | "July 1st,", "Apr 17", "May.9" |
| Day and textual month | d ([ .\t-])* m | "1 July", "17 Apr", "9.May" |
| Month abbreviation, day and year | M "-" DD "-" y | "May-09-78", "Apr-17-1790" |
| Year, month abbreviation and day | y "-" M "-" DD | "78-Dec-22", "1814-MAY-17" |
| Year (and just the year) | YY | "1978", "2008" |
| Textual month (and just the month) | m | "March", "jun", "DEC" |
| Description | Format | Examples |
|---|---|---|
| Eight digit year, month and day | YY MM DD | "15810726", "19780417", "18140517" |
| Four digit year, month and day with slashes | YY "/" MM "/" DD | "2008/06/30", "1978/12/22" |
| Two digit year, month and day with dashes | yy "-" MM "-" DD | "08-06-30", "78-12-22" |
| Four digit year with optional sign, month and day | [+-]? YY "-" MM "-" DD | "-0002-07-26", "+1978-04-17", "1814-05-17" |
Note: For the y and yy formats, years below 100 are handled in a special way when the y or yy symbol is used. If the year falls in the range 0 (inclusive) to 69 (inclusive), 2000 is added. If the year falls in the range 70 (inclusive) to 99 (inclusive) then 1900 is added. This means that "00-01-01" is interpreted as "2000-01-01".
Note: The "Day, month and two digit year, with dots or tabs" format (dd [.\t] mm "." yy) only works for the year values 61 (inclusive) to 99 (inclusive) - outside those years the time format "HH [.:] MM [.:] SS" has precedence.
Note: The "Year (and just the year)" format only works if a time string has already been found -- otherwise this format is recognised as HH MM.
Note: It is possible to over- and underflow the dd and DD format. Day 0 means the last day of previous month, whereas overflows count into the next month. This makes "2008-08-00" equivalent to "2008-07-31" and "2008-06-31" equivalent to "2008-07-01" (June only has 30 days).
It is also possible to underflow the mm and MM formats with the value 0. A month value of 0 means December of the previous year. As example "2008-00-22" is equivalent to "2007-12-22".
If you combine the previous two facts and underflow both the day and the month, the following happens: "2008-00-00" first gets converted to "2007-12-00" which then gets converted to "2007-11-30". This also happens with the string "0000-00-00", which gets transformed into "-0001-11-30" (the year -1 in the ISO 8601 calendar, which is 2 BC in the proleptic Gregorian calendar).