“For some ridiculous reason, to which, however, I’ve no desire to be disloyal,
Some person in authority, I don’t know who, very likely the Astronomer Royal,
Has decided that, although for such a beastly month as February,
twenty-eight days as a rule are plenty,
One year in every four his days shall be reckoned as nine and twenty.”
–W.S. Gilbert. The Pirates of Penzance, Act II.
Here’s a news story about other interesting facets of leap year.