MS Access VBA Correct Week Number between years - vba

Question

I need help with this function. I have a table where based on the posting date I need to assign which week it falls on.
Our week starts on Saturday, so this workaround that Microsoft published some years ago -- doesn't work.
Public Function WOY(MyDate As Date) As Integer ' Week Of Year
WOY = Format(MyDate, "ww", vbSaturday, vbFirstFourDays)
If WOY > 52 Then
If Format(MyDate + 7, "ww", vbSaturday, vbFirstFourDays) = 2 Then WOY = 1
End If
End Function
Would appreciate any help.
Thanks
Valglad

Answer 1

I don't think there is a unique solution here because part of the definition of Week is that it starts on Monday: https://learn.microsoft.com/en-us/office/troubleshoot/access/functions-return-wrong-week-number
One answer That is easy to convert is to assume that Each Saturday gets the same Week Number as the following Monday. Adapting the working solution from: https://learn.microsoft.com/en-us/office/troubleshoot/access/functions-return-wrong-week-number#workarounds
Public Function WOY(MyDate As Date) As Integer ' Week Of Year
MyDate = DateAdd("d", 2, MyDate) 'assuming Saturday gets the same weeknumber as the following Monday
WOY = Format(MyDate, "ww", vbMonday, vbFirstFourDays)
If WOY > 52 Then
If Format(MyDate + 7, "ww", vbMonday, vbFirstFourDays) = 2 Then WOY = 1 'borrowing Microsofts solution to handle all edge cases
End If
End Function
This solution is conceptually simple but then 12/28/19 starts week 1 of 2020.

Answer 2

If our week would start on Monday -- the code in my original message
would flip from 52 to 1 without any issues
For this year perhaps, but not for any year.
Thus, the answer is - as Mathieu clearly explained: There is no solution to your question.
It is for a reason, that the ISO 8601 standard was created where week numbering is an important part, as the first and last week may span calendar year boundaries.
You may use any other week numbering system, but most likely it will have shortcomings as you have seen.