This module provides functions that 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 system epoch (Midnight, January 1, 1970 GMT on Unix, for example). This value can be positive or negative, though POSIX only requires support for positive values, so dates before the system's epoch may not work on all operating systems.