Leap Day 2024: Interesting facts, history, and significance of February 29

Leap day, the extra day in February, that knocks at our doors every four year, receives a royal welcome from one and all. Given its once-in-four-years occurrence, the anticipation surrounding February 29 adds to its charm, turning it into an occasion for creating lasting memories and celebrating in diverse ways. However, February 29 isn't just added to our modern-day calendars without a reason. This lovely leap day balances our calendars with Earth's orbit, preventing seasons from drifting out of place and ensuring equinoxes, solstices and all the annual events follow their schedule. Without the existence of leap day, summers may arrive in November and the months will not be able to predict seasons anymore. (Also read: What would happen if we don't have a Leap Day? More than you might think)

Significance of Leap Day

There is an interesting history of why there was a need to add an extra day in the calendar. It took Earth 365.242190 days to orbit the sun while a calendar year has 365 days. The remaining 0.242190 days or 5 hours 48 minutes and 56 seconds had to be adjusted to ensure seasons do not drift and annual events follow their schedule.

Leap year however doesn't come every four years and years divisible by 100 aren't called leap years. Here's the reason. The difference between the calendar years and the sidereal year is 23.262222 hours instead of 24 hours. The addition of leap day can make calendar longer by over 44 minutes and this could against cause seasons to drift. So, leap years don't occur every four years due to the slight discrepancy between our calendar and Earth's orbit, which adds over 44 minutes. Years divisible by 100 are exempt from leap years unless they are also divisible by 400. This ensures our calendar remains in sync with the seasons, preventing significant drift over time.

History of Leap Day and Leap Year

While sun's position was trusted to determine time of harvest and planting in ancient times, over the time, a need to have a centralised calendar emerged. Introduced by Julius Caesar in 45 BC, the Julian Calendar featured an annual extra day, based on an Egyptian concept. However, Caesar's calculation error of 11 minutes per solar year led to an overcorrection of about eight days per millennium, causing seasonal drift. In the 16th century, Pope Gregory XIII addressed this with the Gregorian Calendar, adding leap days in years divisible by four, except those divisible by 100. Yet, years divisible by 400 still get a leap day, which was in order to realign the calendar with the seasons.