Return the ISO Standards Start of the Year in Excel - First Monday of the Year - UDF

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Return the date of the first Monday of any year with this UDF ISO Year function in Excel. This is a really simple and easy to use UDF (user defined function) in Excel. You just input the desired year, in 4 digit format (1996, 2001, etc.) and the function will return the date of the first Monday in that year.

Make sure the cell where the function is located is formatted as a date because the result of the function is a date serial number.

Where to install the macro:  Module

UDF to Return the ISO Standards Start of the Year in Excel - First Monday of the Year

Function ISOYEARSTART(Year As Integer) As Date

Dim WeekDay As Integer
Dim NewYear As Date

NewYear = DateSerial(Year, 1, 1)
WeekDay = (NewYear - 2) Mod 7

If WeekDay < 4 Then
 ISOYEARSTART = NewYear - WeekDay
Else
 ISOYEARSTART = NewYear - WeekDay + 7
End If

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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