perldoc Time::Local

part of the Core installation

NAME
       Time::Local - efficiently compute time from local and GMT time
 
SYNOPSIS
           $time = timelocal($sec,$min,$hour,$mday,$mon,$year);
           $time = timegm($sec,$min,$hour,$mday,$mon,$year);
 
DESCRIPTION
       These routines are the inverse of built-in perl functions localtime()
       and gmtime().  They accept a date as a six-element array, and return
       the corresponding time(2) value in seconds since the Epoch (Midnight,
       January 1, 1970).  This value can be positive or negative.
       ...