Creating a function check if a year is a leap year

This simple function checks the year passed in and returns true or false dependent on the year with one line of code

Usage

This simple little function is normally called by other database operation calculating age and year differences.

When you run DATEPART DAYOFYEAR and compare the number of days on 3rd March then a leap year will return one more day, which is correct, but needs to be coded around for calculating someones age.

To get around this, we append this function to one of the dates to subtract one day after February 29.

Get Leap Year

CREATE FUNCTION Dates.GetLeapYear(@Date DATETIME2) RETURNS BIT AS BEGIN
DECLARE @Ret BIT=(CASE WHEN DATEPART(YEAR,@Date)%4<>0 OR (DATEPART(YEAR,@Date)%100=0 AND DATEPART(YEAR,@Date)%400<>0) THEN 0 ELSE 1 END)
RETURN @Ret
END
GO

Test

SELECT  [dbo].[GetLeapYear]('01-01-1900') [1900],
[dbo].[GetLeapYear]('01-01-1901') [1901],
[dbo].[GetLeapYear]('01-01-1902') [1902],
[dbo].[GetLeapYear]('01-01-1903') [1903],
[dbo].[GetLeapYear]('01-01-1904') [1904]

Result

Only 1904 will return true as expected.