What do you know about the leap day?

Leap year: What are they and why do we have leap days?

Every four years February has 29 days instead of 28. Here's why

This year is a leap year, according to the Gregorian calendar iStock

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’.

Here's why:

The Gregorian calendar, the most widely used across the globe, measures a year to be 365 days following the Earth's orbit around the Sun.

However, the Earth's orbit takes 365.24 days to complete its solar orbit and an extra day every four years is added to keep calendar seasons synchronised 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.

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.

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