preferred date format will not stick

Question

I am reading that Excel on Mac OS (Sequoia, OSX 15.3) gets its date format from the Language and Region control panel, which I have set to 2025-01-31.

When I create a new spreadsheet either manually or with an export to CSV from my pretty much every online offering, the date is formatted as 01/31/2025, and when I attempt to change it using the Format menu to 2025-01-31, it does not change at all, it stays at 01/31/2025.

I have added a custom format of yyyymmdd and yyyy-mm-dd but neither of those will work either, the cells just stay the way they were when created or imported.

Is there a solution for this, to permanently make the date format the way I want? I have spend what feels like days opening my spreadsheets in (Apple's) Numbers, converting the date format to 2025-01-31 and then exporting the spreadsheet to Excel, but there must be a better way.

Answer 1

Two fundamental questions:

• What is the present Version Number of your Office software?
• Have you restarted Excel since setting the System Setting?

Your 3rd paragraph strongly suggests that the content was entered as text rather than as a date. Simply applying a different format will not convert the text string back to a value. It will remain seen as text regardless of which Number format might be indicated. If so, the data will have to be converted or re-entered.