The Pirates of Penzance (http://en NULL.wikipedia NULL.org/wiki/The_Pirates_of_Penzance); or, The Slave of Duty, is a comic opera (http://en NULL.wikipedia NULL.org/wiki/Comic_opera) in two acts, with music by Arthur Sullivan (http://en NULL.wikipedia NULL.org/wiki/Arthur_Sullivan) and libretto by W.S. Gilbert (http://en NULL.wikipedia NULL.org/wiki/W NULL._S NULL._Gilbert). The opera’s official premiere was on December 31, 1879.
The story concerns Frederic, who, having completed his 21st year, is released from his apprenticeship to a band of tenderhearted pirates. He meets Mabel, the daughter of Major-General Stanley, and the two young people fall instantly in love. Frederic finds out, however, that he was born on February 29, and so, technically, he only has a birthday each leap year (http://en NULL.wikipedia NULL.org/wiki/Leap_year). His apprenticeship indentures state that he remains apprenticed to the pirates until his 21st birthday, and so he must serve for another 63 years. Mabel agrees to wait for him faithfully.