Leap years are needed to keep our modern day Gregorian calendar in alignment with the Earth’s revolutions around the sun.
It takes the Earth approximately 365.242189 days – or 365 days, 5 hours, 48 minutes, and 45 seconds – to circle once around the Sun.
So in 4 years we get 1460.99 which is one day extra in four years.
The next leap year will be on 2020.
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