From Date::Simple(3) man page:

Dates are complex enough without times and timezones. This module may be used to
create simple date objects. It handles:

Validation:
    Reject 1999-02-29 but accept 2000-02-29.
Interval arithmetic:
    How many days were between two given dates? What date comes N days after
    today?
Day-of-week calculation:
    What day of the week is a given date?

It does NOT deal with hours, minutes, seconds, and time zones.

WWW: http://search.cpan.org/dist/Date-Simple/