Return the ISO Week Number from a Date in Excel - UDF

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Return the ISO Week Number in Excel with this UDF. This is a simple to use UDF (user defined function) that returns the number of the week in the year that a specific date occurs.

Where to install the macro:  Module

UDF to Return the ISO Week Number from a Date in Excel

Function ISOWEEKNUMBER(InDate As Date) As Long

Dim D As Date

D = DateSerial(Year(InDate - WeekDay(InDate - 1) + 4), 1, 3)

ISOWEEKNUMBER = Int((InDate - D + WeekDay(D) + 5) / 7)

End Function








How to Install the Macro
  1. Select and copy the text from within the grey box above.

  2. Open the Microsoft Excel file in which you would like the Macro to function.

  3. Press "Alt + F11" - This will open the Visual Basic Editor - Works for all Excel Versions.  Or For other ways to get there, Click Here.

  4. On the new window that opens up, go to the left side where the vertical pane is located. Locate your Excel file; it will be called VBAProject (YOUR FILE'S NAME HERE) and click this.

  5. If the Macro goes in a Module, Click Here, otherwise continue to Step 8.

  6. If the Macro goes in the Workbook or ThisWorkbook, Click Here, otherwise continue to Step 8.

  7. If the Macro goes in the Worksheet Code, Click Here, otherwise continue to Step 8.

  8. Close the Microsoft Visual Basic Editor window and save the Excel file. When you close the Visual Basic Editor window, the regular Excel window will not close.

  9. You are now ready to run the macro.


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