FWIW, the DateTime can translate an object to a string using strftime formats as well. (It's also got a guide to strftime formatting keys in the pod.) Plus with DateTime::Format::Strptime you can use the same format to parse a string into a DateTime object. It also does tons of other hugely useful date stuff.
Check out the theoryx repository (which you can add with the URL: 'http://theoryx5.uwinnipeg.ca/cgi-bin/ppmserver?urn:/PPMServer58') -- the versions they have seem to be a little old, but it's still better than POSIX...