Gilbert and Sullivan’s Pirates of Penzance

The story concerns Frederic, who, having completed his 21st year, is released from his apprenticeship to a band of tender-hearted pirates. He meets the daughters of Major-General Stanley, including Mabel, and the two young people fall instantly in love. Frederic soon learns, however, that he was born on the 29th of February, and so, technically, he has a birthday only once each leap year. His indenture specifies that he remain apprenticed to the pirates until his "twenty-first birthday", meaning that he must serve for another 63 years.  Bound by his own sense of duty, Frederic's only solace is that Mabel agrees to wait for him faithfully.