SQL dateTime, date

create function DateOnly(@DateTime DateTime)
-- Returns @DateTime at midnight; i.e., it removes the time portion of a DateTime value.
returns datetime
as
begin
return dateadd(dd,0, datediff(dd,0,@DateTime))
end
go

create function Date(@Year int, @Month int, @Day int)
-- returns a datetime value for the specified year, month and day
-- Thank you to Michael Valentine Jones for this formula (see comments).
returns datetime
as
begin
return dateadd(month,((@Year-1900)*12)+@Month-1,@Day-1)
end
go

create function Time(@Hour int, @Minute int, @Second int)
-- Returns a datetime value for the specified time at the "base" date (1/1/1900)
-- Many thanks to MVJ for providing this formula (see comments).
returns datetime
as
begin
return dateadd(ss,(@Hour*3600)+(@Minute*60)+@Second,0)
end
go

create function TimeOnly(@DateTime DateTime)
-- returns only the time portion of a DateTime, at the "base" date (1/1/1900)
returns datetime
as
begin
return @DateTime - dbo.DateOnly(@DateTime)
end
go

create function DateTime(@Year int, @Month int, @Day int, @Hour int, @Minute int, @Second int)
-- returns a dateTime value for the date and time specified.
returns datetime
as
begin
return dbo.Date(@Year,@Month,@Day) + dbo.Time(@Hour, @Minute,@Second)
end
go