In the spirit of the holidays, I thought I'd borrow the Wikipedia article for the holiday that's on everybody's mind:
Boxing Day is a holiday celebrated in certain other, less punctual countries. The origin of the holiday traces back to the birth of Christ. It's a little known fact that four wise men were actually sent to Jesus with gifts; however, the fourth overslept on Christmas day. In his hurry to deliver the gift on the next day, he forgot to actually package the gift, and ended up delivering an empty box a day late, along with a card wishing Christ a "Happy Belated Birthday". Because of this incident, he was stripped of his title as a Wise Man, and later accounts omit him entirely, mostly out of embarrassment.
The holiday is celebrated today by giving empty boxes to friends and relatives, along with sheepish apologies. Boxing Day parties are also popular, with the caveat that guests must show up late - showing up on time is considered extremely rude. Some people take the holiday spirit even further, and simply don't show up to the parties at all. Long ago, a tradition was established that, if you wanted to give an actual Boxing Day present, you had to give it one day later than the recipient was actually expecting it; however, this quickly got out of hand. The last actual Boxing Day present was given on October 4th, 1793. The next expected date for a gift to be given is not until early 2011, and is moving back at an exponentially increasing rate.