I have a table with month headers at the top:

January | February | March | ...

Is there a way with one formula that I can get a list of month numbers?

January | February | March | ...
      1 |        2 |     3 | ...

I saw this answer about turning a month string into a month number with =MONTH(DATEVALUE(A1 & " 1")) but when I tried to do =ARRAYVALUE(MONTH(DATEVALUE(A1:1 & " 1"))) it didn't work. In fact MONTH(DATEVALUE(A1:1 & " 1")) gives the same result as MONTH(DATEVALUE(A1 & " 1")).

1 Answer 1


There is no arrayvalue command; there is arrayformula.

Yes, MONTH(DATEVALUE(A1:1 & " 1")) gives the same result as MONTH(DATEVALUE(A1 & " 1")) because without arrayformula, it expects one value as an argument. Given more, it only takes the first one.

The correct formula (tested in my spreadsheet) is

  • Oh whoops. I meant ARRAYFORMULA. I just tried it in a new sheet and it worked, but it's not working in a different sheet I have. There must be some sort of collision happening. Commented Jan 9, 2016 at 21:38
  • 1
    Sometimes the data present in the sheet prevent the output of arrayformula from expanding. Also, consider whether you really need A1:1 - presumably there are just 12 months, so A1: L1 would be enough.
    – user79865
    Commented Jan 9, 2016 at 22:14

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