I didn't mean to imply that Date::Manip wouldn't work. I know that it will work fine. I will, however, admit that my advice could have been more detailed.

Date::Manip is an old module. Even it's author says that it is usually the wrong module to use. The most common criticisms of it are that it is large and slow. Personally, my biggest criticism of it is that it doesn't play well with others. The DateTime family of modules all work together well. If you're doing any work with dates and times then I really think that they should be the first place that you look.