Unix in a Nutshell, 4th Edition

Legal Date Formats

The legal time and date formats for CVS are defined by the ISO 8601 standard and RFC 822 as amended by RFC 1123. Other formats can be interpreted, but CVS is designed to handle only these standards.

ISO 8601

The basic ISO 8601 date format is as follows:

year-month-day hours:minutes:seconds

All values are numbers with leading zeros to ensure that the correct number of digits are used. Hours are given in 24-hour time. This produces the structure YYYY-MM-DD HH:MM:SS, which is internationally acceptable and can be sorted easily. You can use a date, a time, or both.

If you’re using ISO 8601 format with the hyphens, the full date is required in CVS. The YYYYMMDD date format is also acceptable and can be abbreviated to YYYYMM or YYYY.

The HH and HH:MM time formats are acceptable. Times can also be specified without the colon, so HHMMSS or HHMM are usable.

Warning

Be aware that HHMM may be misinterpreted as YYYY. Get into the habit of using separators.

In strict ISO 8601 format, a T is required between the date and the time, but CVS understands this format with or without the T. The ISO 8601 standard also states that a Z at the end of the string designates UTC (Universal Coordinated Time), but CVS does not recognize the use of Z.

RFC 822 and RFC 1123

RFCs 822 and 1123 define a precise time format:

    [DDD ,] DD MMM YYYY HH:MM[:SS]ZZZ

These are the terms in the format:

DDD	A three-letter day of the week.
DD	A two-digit date of the month.
MMM	A three-letter month.
YYYY