You might be interested in my HTML::CalendarMonth. It supports many locales and a variety of date computation sources: Time::Local, DateTime, Date::Calc, Date::Manip, and the unix 'cal' command.

basic usage:

$c = HTML::CalendarMonth->new( month => 10, year => 1980 );
print $c->as_HTML;
[download]

It's actually a tree structure made of HTML::Element nodes, so if you're using that it's a natural fit. You can alter the attributes or add/change content to each node before generating the HTML.

Cheers,
Matt