WEEKNUM Returns the week number for the given date and year according to the return_type value. The week number indicates where the week falls numerically within a year.
Syntax
WEEKNUM(date, return_type)
Parameters
date – The date in datetime format.
return_type – A number that determines the Return value: use 1 when the week begins on Sunday; use 2 when the week begins on Monday. The default is 1.
Return type: 1, week begins on Sunday. Weekdays are numbered 1 through 7.
Return type: 2, week begins on Monday. Weekdays are numbered 1 through 7.
Return Value
An integer number.
Reference Data
https://docs.microsoft.com/en-us/dax/dax-function-reference