3.7.1. Problem

3.7.2. Solution

If your date is already numeric, or in a rigid and easily parsed format, use a regular expression (and possibly a hash mapping month names to numbers) to extract individual day, month, and year values, and then use the standard Time::Local module's timelocal and timegm functions to turn that into an Epoch seconds value.

use Time::Local;
# $date is "2003-02-13" (YYYY-MM-DD form).
($yyyy, $mm, $dd) = ($date =~ /(\d+)-(\d+)-(\d+)/);
# calculate epoch seconds at midnight on that day in this timezone
$epoch_seconds = timelocal(0, 0, 0, $dd, $mm-1, $yyyy);

use Date::Manip qw(ParseDate UnixDate);
$date = ParseDate($STRING);
if (!$date) {
    # bad date
} else {
    @VALUES = UnixDate($date, @FORMATS);
}

3.7.3. Discussion

The flexible ParseDate function accepts many formats. It even converts strings such as "today", "2 weeks ago Friday", "2nd Sunday in 1996", and "last Sunday in December", plus it understands the date and time format used in mail and news headers. It returns the decoded date in its own format: a string of the form "YYYYMMDDHH:MM:SS". You could compare two such strings to compare the dates they represent, but arithmetic is difficult. We therefore use the UnixDate function to extract the year, month, and day values in a preferred format.

use Date::Manip qw(ParseDate UnixDate);

while (<>) {
    $date = ParseDate($_);
    if (!$date) {
        warn "Bad date string: $_\n";
        next;
    } else {
        ($year, $month, $day) = UnixDate($date, "%Y", "%m", "%d");
        print "Date was $month/$day/$year\n";
    }
}

3.7.4. See Also