The Pirates of Penzance

Pirate King:
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.

Through some singular coincidence,
I shouldn't be surprised if it were owing to the agency of an ill-natured fairy

You are the victim of this clumsy arrangement,
having been born in leap-year,
on the twenty-ninth of February;

And so, by a simple arithmetical process,
you'll easily discover,

That though you've lived twenty-one years,
yet, if we go by birthdays,
you're only five and a little bit over!

Yep - Gilbert & Sullivan have something to say about Leap Year!