Determine Leap Year

Today is a special day which comes only after four years -29th Feb. So I thought I should write something about leap year.

First, what is leap year?

• The year must be divisible by 4 and must NOT be divisible by 100.
• The year must be divisible by 400.

In some scenario, you need to count the number of days in a year Like Banking application where in savings account interest is calculated based on number of days in year. A year can have 366 days or 365 days based on whether year is Leap or not.

I am writing one user defined function which takes data as parameter and returns 1 if it is leap year and 0 if it is not.

CREATE FUNCTION [dbo].[udf_IsLeapYear] ( @Date    DATETIME )

RETURNS BIT

AS

BEGIN

    IF (YEAR( @Date ) % 4 = 0 AND YEAR( @Date ) % 100 != 0) OR

        YEAR( @Date ) % 400 = 0

        RETURN 1

    RETURN 0

END

GO

Example: How to calculate number of days in year.

DECLARE @DaysInYear INT

SET @DaysInYear = 365 + [dbo].[ufn_IsLeapYear] ( GETDATE() )

print @DaysInYear

It will print 366.