Date::Manip is certainly the most powerful of the Date modules.
    To the best of my knowledge, it will do everything that any
    other date module will do (not just the ones I listed above),
    and there are a number of features that Date::Manip has that
    none of the other modules have. Date::Manip is the "Swiss Army
    Knife" of Date modules. I'm trying to build a library which can
    do _EVERY_ conceivable date/time manipulation that you'll run
    into in everyday life.

    Although I am working on making Date::Manip faster, it will
    never be as fast as other modules. And before anyone asks,
    Date::Manip will never be translated to C (at least by me). I
    write C because I have to. I write perl because I like to.
    Date::Manip is something I do because it interests me, not
    something I'm paid for.

    Date::Manip is also big. The last time I looked, it's one of the
    largest CPAN modules there is. If you ignore modules like Tk,
    LWP, etc. which are actually packages of modules, it may be the
    largest. It's true that Date::Manip will do almost every date
    operation you could imagine... but you rarely need all that
    power. I'm working on reducing the footprint of Date::Manip, but
    even at it's slimmest, it'll outweigh the other modules by a
    good bit.

    If you are going to be using the module in cases where
    performance is an important factor (started up in a CGI program
    being run by your web server 5,000 times a second), you should
    check out one of the other Date or Time modules in CPAN. If
    you're only doing fairly simple date operations (parsing common
    date formats, finding the difference between two dates, etc.),
    the other modules will almost certainly suffice. If you're doing
    one operation very repetitively (parsing 10,000 dates from a
    database), you are probably better off writing your own
    functions (perhaps bypassing all date modules entirely) designed
    specifically for your needs.

    On the other hand, if you want one solution for all your date
    needs, don't need peak speed, or are trying to do more exotic
    date operations, Date::Manip is for you. Operations on things
    like business dates, foreign language dates, holidays and other
    recurring events, etc. are available more-or-less exclusively in
    Date::Manip.