The shortest month of the year, February gets the privilege of an 'extra day' called leap day in every fourth year. Today is again that extra day and which obviously makes this year a special year. February 29 is a date that only rarely graces our lives, but plays an enormously important role-- it keeps our annual calendar and the passing of the seasons aligned over very long timescales.
What is a leap day?
This day is added to the calendar in leap years as a corrective measure because the Earth does not orbit the sun in precisely 365 days. It orbits the Sun 365 days and 6 hours. A year according to the Gregorian calendar, named after Pope Gregory XIII, is 365 days or how long it takes the Earth to orbit the sun. But Earth’s orbit is actually closer to approximately 365.25 days, so without leap days, the calendar would be off by five hours, 48 minutes and 45 seconds more each year. After 100 years, the seasons would be off by 25 days.
A year maybe a leap year if it is evenly divisible by four. Years that are divisible by 100, century years such as 1900 or 2000, cannot be leap years unless they are also divisible by 400. For this reason, the years 1700, 1800 and 1900 were not leap years, but the years 1600 and 2000 were. This rule about years divisible by 100 years and 400 years was added with the introduction of the Gregorian calendar in 1582.
Who are leaplings?
Someone born on a Leap Day is known as a leapling, though the odds of being a leapling are exceedingly slim. The chances of being born on a leap day are about one in 1,461, according to the BBC. Leaplings typically celebrate their birthdays on Feb. 28 or March 1, iNews reports.
Technically, a leapling will have fewer birthday anniversaries than their age in years. This phenomenon is exploited when a person claims to be only a quarter of their actual age, by counting their leap-year birthday anniversaries only.
Are leap days constant?
Right now, we're only adding a single leap second every 18 months or so to accommodate it, the day continues to lengthen. After another 4 million years go by on Earth, the day will lengthen by another 56 seconds--the exact amount necessary for a tropical year to require exactly 365 days.
At that point approaches, we'll want to first reduce the number of Leap Days and later get rid of them altogether, as they'll become completely unnecessary. If humans are still around and keeping calendars at that point, we'll want to think about further transitions, as we're going to need to begin skipping days (in a reverse-Leap Day scenario) in order to keep our seasons aligned with our calendar.
The next leap day will be Thursday, Feb. 29, 2024.