Usually March 14, one month after Valentines. In certain Asian countries Valentines Day is observed by the women, who buy men chocolates, the quality of the chocolate indicative of the mans relationship to her. March 14 is the day the favour is returned, with the gift from the man 2 to 3 times that of the woman's. Read more here. Which could be interpreted as proof that the price of love is high, or simply that they acknowledge that men (generally) make far more than women. Or in any number of other ways, stretch your imagination a bit...
a miscellany of completely unrelated thoughts...