Hmm, I wouldn't use 'sprintf' as a search term for this particular query, I'd choose terms like 'date format' or 'date string' or something. And, while neither of those queries turned up POSIX.pm on either CPAN search engine, both engines did turn up Date::Format with the 'date format' query.

the search.cpan.org query
the theory5x.uwinnipeg.ca/CPAN/cpan-search.html query