New Delhi

Leap Year comes every four years, or so we think. Perhaps we can be forgiven to believe in four-year frequency of the month of February having an extra day. When we were taught the fact during school, we may have been too young to learn about exceptions to the four-year rule.

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The working rule for a year to be called a leap year depends on the days in the month of February. If February has 28 days, its not a leap year. If it has 29, it is a leap year. Pretty clear thing as reflected in last line of the English poem 'Thirty days has September...'

The six-line poem, which finishes off tally for 11 months of the year in just three lines, takes next three just to explain what's the deal with February.

For those preferring mathematical precision than linguistic ramblings, the general test to find out whether a year is a leap year or not, is simple. If the four-digit figure of a particular year is completely divisible by 4, the year is a leap year. If it's not completely divisible by 4 and yields a remainder during the calculation, the year is not a leap year.

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So far so good?

The 'divisible by four' test means that leap years should come every four years. And this is what we normally imagine.

But like that famous Morpheus meme from Matrix, what if I told you that what you believed your whole life about leap years is...well, not a lie but rather an incomplete truth?

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Unnecessary dramatic effects aside, the commonly held rule about leap years has exceptions.

What's the exception to the four-year rule of leap year?

If a year is divisible by 4, it is not a test enough for it to grab the tag of a leap. If it is divisible by 4 but is also divisible by 100, the year is not a leap year. This is why years 1800 and 1900 were NOT leap years.

But what about year 2000? The dreaded Y2K was a leap year for sure.

Yes, year 2000 was a leap year.

This is an exception to the rule described above (stay with us).

So if a year is divisible by 4 but also by 400, then it becomes a leap year even if it is divisible by 100.

Take a deep breath, read it again. It's pretty simple. Happy leap year to you!

(With inputs from agencies)