I would encourage you to use the far more powerful OO interface in Date::Manip rather than the older functional interface.

Instead of using DateCalc, use the calc method (and see here for the full description of date calculations.

Instead of using Delta_Format, use the printf method (and see here for a full description of delta formatting).

Of course, if you already have a script that uses the functional interface, it may not be worth the effort to change it.