The DateTime.pm module aims to provide a complete, correct, and easy
to use date/time object implementation.  Currently it handles many date
calculations, date math (addition and subtraction), and provides
convenient methods for retrieving portions of a date/time.

This module properly supports the Olson time zone database, meaning
that historical time zone information, and more importantly, daylight
saving time rules, can be handled transparently, simply by setting the
correct time zone.  This is done by using the DateTime::TimeZone
module.