This module allows you to do nominal math on dates. That is, rather
than worrying about time zones and DST while adding increments of
24*60**2 seconds to a date&time object, you simply discard the time
component and do math directly on the date. If you need a time-of-day
on the calculated date, the at() method returns a Time::Piece object,
thus allowing you to be specific about the endpoints of a nominal interval.