Perl has a great core module for dealing with dates and times: Time::Piece.

use Time::Piece;

my $t = localtime();

my $unixtime = $t->epoch(); # Unixtime
my $human    = $t->cdate(); # Human readable

# Format a date/time for output
print $t->strftime("%Y-%M-%d") . "\n";

# Convert a specific format to a date/time object
my $bd = localtime->strptime("1985-02-14", "%Y-%M-%d");
print "You were born on a " . $bd->fullday . " in " . $bd->year . "\n";

# Date/Time addition
print "In one hour it will be: " . (localtime() + 3600)->hms . "\n";

It works by overriding the built in localtime() and gmtime() functions and giving them an object oriented interface. I highly recommend looking at it if you have to deal with dates and times.