Nearly every four years, the Gregorian calendar — which is used in the majority of countries around the world — gets an extra day: February 29.
For some people, leap day means frog jokes and extravagant birthday parties. For many, it may conjure memories of the 2010 rom-com Leap Year, which harkens back to the Irish tradition by which women can propose to men on that one day. And others likely see it merely as a funny quirk in the calendar, or just another Thursday.
Leap day means several different things to Alexander Boxer, a data scientist and the author of A Scheme of Heaven: The History of Astrology and the Search for Our Destiny in Data.
Literally speaking, he says, it's an "awkward calendar hack" aimed at making up for the fact that a year isn't a flat number of days, but more like 365 and a quarter. But there's more to it than that.