Ok, first of all why we need to check if a year is leap
year or not?

Answer is simple! A leap year contains an extra day
(i.e. 29

^{th}February).
So, as per my conclusion if we select a date from a leap
year and before 1

^{st}March i.e. in between 1^{st}January & 29^{th}February (both dates including) then we need to go one day back from the day we calculated to get the exact day!
Didn't get the thing???? Don’t worry; you will be clear with it as I will explain
it with an example in the next chapters.

First we will see how to find if a year is a leap year
or not. And it is simple to find one. For that you will have to check if last
two digits in a year (YY

__YY__) are 00 or not. Based on that following are the two cases to know if a year is leap year or not:**Case 1.**If last two digits in year are other than 00

If last two digits in year are other
than 00 (as in 1996) then check if the number formed by these

**last**two digits (96) is completely divisible by 4 i.e. remainder is zero (or we can say these last two digits form a number that is present in the multiplication table of 4).
If above condition is true then the
given year is a leap year.

**Example:**1996 is a leap year as 96 is completely divisible by 4 i.e. remainder is zero (96 is present in the multiplication table of 4).

If above condition is false then the
given year is not a leap year.

**Example:**1997 is not a leap year as 97 is not completely divisible by 4 i.e. remainder is not zero (97 is not present in the multiplication table of 4).

**Case 2.**If last two digits in year are 00

If last two digits in year are 00 (as
in 2000) then check if the number formed by

**first**two digits (20) in the year is completely divisible by 4 i.e. remainder is zero (or we can say these last two digits form a number that is present in the multiplication table of 4).
If above condition is true then the
given year is a leap year.

**Example:**2000 is a leap year as 20 is completely divisible by 4 i.e. remainder is zero (20 is present in the multiplication table of 4).

If above condition is false then the
given year is not a leap year.

**Example:**2100 is not a leap year as 21 is not completely divisible by 4 i.e. remainder is not zero (21 is not present in the multiplication table of 4).

Now, we will summarize above two
cases:

**Case 1.**If year is like YYYY (i.e. last YY are not 00) then–

Check if

**last**YY (YY__YY__) is completely divisible by 4.
If yes then YYYY is a leap year.

If no then YYYY is not a leap year.

**Case 2.**If year is like YY00 (i.e. last YY are 00) then–

Check if

**first**YY (__YY__YY) is completely divisible by 4.
If yes then YYYY is a leap year.

If no then YYYY is not a leap year.

That is to it!

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