I'd learn how to install modules.

CPAN Modules are neat -- you can install them server side if you have root privs, or you can just install them into your local directory

I'd strongly suggest running the cpan shell ( $perl -MCPAN -e shell ) , then upgrading cpan ( install Bundle::CPAN ) and following the instructions to restart the shell and install modules away. Once you get comfortable with that, you can su/sudo to root and install system-wide -- or not.

Date::Calc is really the best thing you can use for this situation. It's fast and takes into consideration all of the crazy issues that other people have encountered.