Once again I repeat my recommendation for Time::Piece. It's also worth noting that of all the Date/Time modules, this is the one that is most likely to make it into the core distribution (it was going to be in 5.8, but was removed at the last minute).

I should also point out this section from the documentation for Date::Manip

SHOULD I USE DATE::MANIP

If you look in CPAN, you'll find that there are a number of Date and 
Time packages. Is Date::Manip the one you should be using? In my 
opinion, the answer is no most of the time. This sounds odd coming 
from the author of the software, but read on.

Date::Manip is written entirely in perl. It's the most powerful of the
date modules. It's also the biggest and slowest.
[download]

For this reason, I avoid Date::Manip most of the time.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg