This would be a good time to point out the Should I Use Date::Manip section in the docs, which starts off:

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.

Follow the link above to read the authors full statement.

-Blake