What is a Leap year?
Normally our calendar years are made up of 365 days, but every four years we add a day to make what is known as a ‘leap year’. The Gregorian calendar (the calendar we are using now) measures a year to be 365 days following the Earth’s orbit around the Sun.
However, for students who have started taking Science, you would have learnt that the Earth’s orbit takes 365.25 days to complete its solar orbit. By omitting 0.25 days each year, after 4 years, the 0.25 days would accumulate to make up one full day, resulting in this extra day every 4 years. This was done to ensure our calendar seasons are synchronized with solar seasons.
If we didn’t do this the seasons would shift around the calendar, and in 750 years’ time June would find itself in the middle of winter. By inserting an additional day into the year, the inaccuracy can be corrected.
Fun facts about the modern calendar
The origins of the modern calendar as we know it date back to the Roman times. Julius Caesar introduced the Julian calendar in 46 BC, which consists of 365 days with 366 in every fourth year.
However, in his calendar February had 30 days and August 29. When Caesar Augustus became emperor he changed this so “his” month had the same amount as Caesar’s. He reduced February to 28 days to accommodate the amendment.
In 1582 the UK switched to the Gregorian calendar and worked out the Julian Calendar didn’t actually reflect the actual time the Earth takes to orbit the sun, or tropical year.
The Gregorian calendar follows three rules to determine which years are leap years: if the year can be divided by four it is a leap year, but if it can be evenly divided by 100 or by 400 then it is not.
Despite this complicated process the calendar is still not perfect, every 3,236 years it will be out by a day.
Comparably, the Julian calendar is currently lagging behind the Gregorian calendar by 13 days.
Leap day birthdays
For people who are born on 29 February, you are a leap day baby! There are approximately 4.8 million people in the world who were born on leap day. Nope, they do not celebrate only once every 4 years. But they do only get to celebrate on their actual birth day once every 4 years. So… Happy birthday!