SQL Week of Month without DATEFIRST - sql-server

Question

I am working with dates so I have created a function that generates a SQL Table Calendar which returns Day, Month, WeekOfMonth, WeekOfYear and so on.
Right now, for the Day of Month field I am using the following function:
-- [WkNo]=Week number
[WkNo] = DATEPART(week,dt.DT),
But the problem is that when I run this on a SQL installed with Language = US English, the week setting is wrong cause the week starts from Sunday.
I need to set the week starting from Monday, is it possible without the use of DATEPART?

Answer 1

Update: based on asker's comment that he cannot use the DATEFIRST approach I am updating answer.
Note:
This answer is generic in nature.
If instead of Monday you want the week to start from Tuesday, you can change the dateadd(dd,-1,dt.DT) to dateadd(dd,-2,dt.DT) and for Wednesday to dateadd(dd,-3,dt.DT).
Basically the formula becomes dateadd(dd,-n,dt.DT) for value of n ranging over 1(Monday) to 6 (Saturday).
SELECT [WkNo]=
ISNULL(DATEPART(week,
case
when Year(dt.DT)>YEAR(dateadd(dd,-1,dt.DT))
then null
else dateadd(dd,-1,dt.DT)
end
),1)
See working fiddle http://sqlfiddle.com/#!6/10a80/14
Old Answer:
See MSDN documentation: https://msdn.microsoft.com/en-us/library/ms174420.aspx
When datepart is week (wk, ww) or weekday (dw), the return value
depends on the value that is set by using SET DATEFIRST. January 1 of
any year defines the starting number for the week datepart, for
example: DATEPART (wk, 'Jan 1, xxxx') = 1, where xxxx is any year.
SET DATEFIRST 1
-- [WkNo]=Week number
[WkNo] = DATEPART(week,dt.DT),

Answer 2

try
SET DATEFIRST {1,2,3,4,5,6,7(default, U.S. English)}
for your Query:
set datefirst 1
select [WkNo]= DATEPART(week,dt.DT)
See Here