Custom format for cell not working properly

Copper Contributor

I have set cell C3 to custom format mm.yy;;; but when i enter the date '02.24' it changes the cell to '01.00'. It is working for other cells on this sheet.


From what I have read, this may be excel thinking mm is minute however this should only happen if a h is present before the m. In my case there is no h and yet it will not format my cell to be the custom date format that I need (mm/yy). 


My language is appropriately set to English - UK. 

2 Replies

Hi @emmadiagenics,

the problem is that the custom format mm.yy;;; is not unambiguous. It could be interpreted as either a date format or a number format, depending on the context. In your case, Excel is interpreting it as a number format.

To fix this, you need to add a [Date] prefix to the custom format. This tells Excel that the format should be interpreted as a date format. The updated custom format would be [Date]mm.yy;;;.

To apply the updated custom format, follow these steps:

  1. Select cell C3.
  2. On the Home tab, in the Number group, click the Format dropdown menu.
  3. Select Custom.
  4. In the Type box, enter the following custom format:




  1. Click OK.

Now, when you enter the date 02.24 into cell C3, it will be formatted correctly as 02.24.

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Kindest regards,

Leon Pavesic

Thank you, but it didn't solve the issue.

When I added [Date], excel would not allow me to hit ok and the pop up reads 'Microsoft Excel cannot use the number format you typed. Try using one of the built-in number formats.'