From the same Gilbert & Sullivan: the Pirate King's chant:

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!