“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.