There is always something to do in New York. Even on a weekday afternoon you can find a place to party. Many locals go out after their 9 to 5 work.
But if you like to party in New York, save your energy. The best discos in the world are in New York. And on weekends the party starts early and ends late. The offer of places to go is so varied (and changing) that everyone will find a favorite place.