POSIX time format
In POSIX time format, the timestamp should be in the form [[CC]YY]MMDDhhmm[.SS] where each pair of letters represents the following:
CC The first two digits of the year (the century). YY The second two digits of the year. MM The month of the year, from 1 to 12. DD the day of the month, from 1 to 31. hh The hour of the day, from 0 to 23. mm The minute of the hour, from 0 to 59. SS The second of the minute, from 0 to 59.
If the CC and YY letter pairs are not specified, the values default to the current year. If the SS letter pair is not specified, the value defaults to 0.
10:00 AM on Aug 23 2004: 200408231000 11:30 PM on Sep 01 2006: 200609012330 12:00 PM on this Oct 09: 10091200
Some utilities which require POSIX time, such as the at scheduler, will also understand a time specified with no date at all; or may understand esoteric keywords such as now, noon, midnight, etc. But none of those are actually part of the POSIX time standard; the standard itself requires month, day, hour, and minutes, with century, year, and seconds optional.