Here's how they extend Valentine's Day in Japan and Korea. (Thanks to my friend in Japan for cluing me in to these!)
In Japan, girls give boys chocolate on Valentine's day. White Day (March 14th) is the boys day to reciprocate. The generally recited rule is that the return gift should be two to three times the cost of the Valentine's gift. Sounds good to me!
If you didn't get to celebrate Valentine's Day or White Day, you celebrate Black Day (April 14th). Basically, you go to a restaurant with similarly single friends and eat white noodles with black bean sauce. Wish I'd know about this holiday when I was single! I might celebrate it anyway, just for fun.