Programming Perl, 4th Edition

gmtime

gmtime EXPR
gmtime

This function converts a time as returned by the time function to a nine-element list with the time correct for what was historically called Greenwich Mean Time (GMT), but which is now known as Coordinated Universal Time (UTC). It’s typically used as follows:

#  0    1    2     3     4    5     6     7     8
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = gmtime;

If as here the EXPR is omitted, it does gmtime(time()). The Perl library module Time::Local contains a subroutine, timegm, that can convert the list back into a time value.

All list elements are numeric and come straight out of a struct tm (that’s a C programming structure—don’t sweat it). In particular, this means that $mon has the range 0..11, with January as month 0, and $wday has the range 0..6, with Sunday as day 0. You can remember which ones are zero-based because those are the ones you’re always using as subscripts into zero-based arrays containing month and day names.

For example, to get the current month in London, you might say:

$london_month = (qw(Jan Feb Mar Apr May Jun
                    Jul Aug Sep Oct Nov Dec))[(gmtime)[4]];

$year is the number of years since 1900; that is, in year 2023, $year is 123, not simply 23. To get the four-digit year, just say $year + 1900. To get the two-digit year (for example “01” in 2001), use sprintf("%02d", $year % 100).

In scalar context, gmtime returns a ctime(3)-like string based on the GMT time value. The Time::gmtime module supports a by-name interface to this function. See also POSIX::strftime ...