in reply to Re^6: date and time difference
in thread date and time difference

"timegm_modern" is not exported by the Time::Local module

That function wasn't added to Time::Local until version 1.27; Perl 5.8.7 shipped with version 1.11. In all three cases, the best option is to update/install the modules.

And the bad "solution" is to use timegm instead of timegm_modern. In that case, at least prefix it with die "Bad year $year" unless $year>1000;.