Yeah, testing kinda moved past use_ok. As Test2::Bundle::More states, "These are not necessary. Use use and require directly." It's a show stopping fatal error if the module you're testing can't be used at all so wrapping it in an eval to make it non-fatal and then writing more code to bail out if that test failed because the following tests would also likely fail as well was kinda iffy.

Back on topic, just so we have a starting place to figure out why you're getting unexpected values, try something like this to get the version of Date::Manip installed on your live environment (which is hopefully still up and running and not also the dev machine upgraded to 5.38.x...):

perl -MDate::Manip -e 'warn $Date::Manip::VERSION'

There's been a lot of time delta related changes in https://metacpan.org/dist/Date-Manip/changes since perl 5.10 was released. Hopefully we can narrow the range down a little with a version number. Class::MethodMaker might as well be magic the way it generates methods around other OOP modules so that'll be the last thing I'd try to dig into.