Simple Way To Determine The Number Of Days In A Month For Any Given Date

DECLARE @varDate datetime
DECLARE @varMonthDate datetime
DECLARE @varYear datetime
DECLARE @varFOM varchar(10)
DECLARE @NumDaysInMonth as int

select @varDate = '2/1/2004'

select @varMonthDate = MONTH(@varDate)
select @varYear = YEAR(@varDate)
select @varFOM = CAST(CAST(@varMonthDate as int) as varchar) + '/1/' +
CAST(CAST(@varYear as int) as varchar)
select @NumDaysInMonth = DATEDIFF (day,@varFOM,DATEADD(mm,1,@varFOM))

select @NumDaysInMonth as DaysInMonth