Function to find Day in a month

Hi ,

This function is used to find out the total no .of days in the month.

Create Function getday
(

@day datetime
)
Returns int
As
Begin

Return case 
    When month(@day) in (1,3,5,7,8,10,12) then 31
    When month(@day) in (4,6,9,11) then 30
Else case 
when (year(@day)%4=0 and 
year(@day)%100!=0) or 
(year(@day)%400=0)
then 29
End
End
End

Select dbo.getday('2012-02-20')