The only module that I even consider for anything to do with dates and times these days is DateTime, because I never need to just print the current time with a fancy format. I always need to do at least some manipulation of it, or can envisage having to do that in the future. And if you use anything else for date/time arithmetic you are in a state of sin.

I've not looked in depth at its implementation of strftime, but from a quick glance at the source it appears to be its own pure-perl implementation, so even if it has bugs I've not noticed at least they should be portable bugs :-)