Gilbert and Sullivan’s The Pirates of Penzance revolves around the fact that Frederick the pirate apprentice is indentured to serve till his ‘one and twentieth’ birthday. Unfortunately, he was born on leap day, which means “That birthday will not be reached by you till nineteen-forty” and he is only “five and a little bit over”. (Actually, the text only says that he was born in “leap year”, but it’s clear that he was born on leap day.)
There has been some discussion as to whether Gilbert didn’t know, forgot or didn’t care that 1900 was not going to be a leap year, in which case the story takes place in 1877, or he knew and cared, in which case it’s 1873. The musical premiered in 1879, but the Major-General boasts about being able to “whistle all the airs from that infernal nonsense, Pinafore“, referring to G&S’s previous musical HMS Pinafore. That premiered in 1878, Gilbert started writing the text in late 1877 and Sullivan wrote the music in early 1878, which makes it very unlikely that someone would know “all the airs” in 1877, but absolutely impossible in 1873. (Issac Asimov wrote a short story to this effect.)
The other problem with time in this musical is that the Major-General’s daughter’s plan to take off their shoes and stockings and paddle in the ocean … on 1 March … in Cornwall.