In Will Gluck's new rom-com, premarital sex is only legal one night each year. Guess when our would-be lovebirds meet? Admittedly, this one took me a minute to parse. When exactly is the least romantic night of the year ? That question is key, because that’s when Will Gluck ‘s ( “Anyone but You,” “Easy A,” rom-com king ) latest, “ One Night Only ,” is set. New Year’s Eve? Valentine’s Day? Tax Day? Alas, the fun and flirty looks on display in the film ‘s first trailer sure don’t scream “WINTER