Forum Discussion
Custom Date format Excel 365 ddd/mm/yy
Unfortunately, Excel for Web currently does not support creating or editing custom number/date formats (as far as I know).
You can only select from the pre-defined list of formats under “Number Format → Date.”
This is a known limitation — even though the web app preserves existing custom formats created in the desktop app.
So if you try to type ddd - dd mmm - yy (or your desired Mon - 01 Jan - 25) directly in the web UI, it won’t accept it.
Workarounds:
Use a helper column with a TEXT formula
If you want to stay fully within Excel for Web, use a formula instead:
=TEXT(A2, "ddd - dd mmm - yy")
Then your output will look exactly the same, e.g.:
Mon - 01 Jan - 25
You can even hide the raw date column and just display this formatted version in your to-do list.
This is dynamic — if you change the date in A2, the formatted result updates automatically.
Use a helper column with a TEXT formula
If you want to stay fully within Excel for Web, use a formula instead:
=TEXT(A2, "ddd - dd mmm - yy")
Then your output will look exactly the same, e.g.:
Mon - 01 Jan - 25
You can even hide the raw date column and just display this formatted version in your to-do list.
This is dynamic — if you change the date in A2, the formatted result updates automatically.
This is a suggestion.
My answers are voluntary and without guarantee!
Hope this will help you.