2nd February, according to the 2nd definition below.
Film of the 1980s, starring Bill Murray as a weatherman who rather reluctantly goes to report on a rather quaint little custom- Groundhog Day, which takes place once a year on 2nd February in a "tiny hamlet [called Punxsutawney] in western Pennysylvania, blah-bla-bla-bla-blah". The trouble is, he can't leave. Not just because of a blizzard on the 2nd February, but also because, when he wakes up again, it's the 2nd February again. And again. And again. The film's weakness is the usual Hollywood moralising from the skies "Be nice, make other people's lives worth living, and then the plot will allow you to live yours... be a calculating Miserable OFB, and things will just get worse". The film's strength though, is a very good piece of lead characterisation, showing a fairly accurate (well, as far as I know...) depiction of how someone would respond to this sort of metaphysical trap.
Day in which television stations across the English-speaking world will show the film of the second definition with a sort of terrible predictability.