The ball drop started in England, but the Times Square thing started 100 years ago, so this is a sort of special date all in all.
It's a new ball every time and it's sort of interesting to see how much heavier or lighter it grows with developing technology.
This is a cool time line of the Ball, showing some nice facts and trivia in a comprehensible way:
http://cache.gizmodo.com/assets/resources/2007/12/timeball-timeline2.jpg
