2024 is finally here, and it's no ordinary year — it's a leap year. But what are leap years? Why do we need them? And how did they come about?
In addition to leap years and leap days, the Gregorian calendar also has a handful of leap seconds, which have sporadically been added to certain years — most recently in 2012, 2015 and 2016. However, the International Bureau of Weights and Measures , the organization responsible for global timekeeping, will abolish leap seconds from 2035 onward.
If we did not account for this difference, then for each year that passes the gap between the start of a calendar year and a solar year would widen by 5 hours, 48 minutes and 56 seconds. Over time, this would shift the timing of the seasons. For example, if we stopped using leap years, then in around 700 years the Northern Hemisphere's summer would begin in December instead of June, according to the National Air and Space Museum.
The history of leap years The idea of leap years dates back to 45 B.C. when the Ancient Roman emperor Julius Caesar instituted the Julian calendar, which was made up of 365 days separated into the 12 months we still use in the Gregorian calendar.