date formatting not correct, even though i have English US selected

To override the default Date format, try this method.

Select the Cells in Excel, right click them and select Format Cells.

Do not click Date on the left, click Custom.

Replace the General text in the box indicated below with mm/dd/yyyy

Apply that setting by clicking OK.

Then enter a date into one of the cells to test if it is formatted correctly.

Windows regional settings control how dates are displayed in many apps, but each app can also apply its own date format. If the format keeps reverting to spaces instead of slashes, verify both the Windows regional settings and the application’s own date format.

1. Confirm Windows regional settings
   1. Open Control Panel.
   2. Select Region (or Clock, Language, and Region > Region).
   3. On the Formats tab, ensure Format is set to English (United States).
   4. Select Additional settings… and check the Date tab to confirm the Short date is set to MM/dd/yy (with slashes).
   5. Apply and OK all dialogs.
2. Check the app’s date format
   • Some Microsoft apps (for example, Access, Project, or form controls like date pickers) can override the Windows format.
   • In those apps, open their Options or formatting dialog and explicitly select the desired date format with slashes.
   • If the app uses a date picker or text box control, open its properties and choose a date format that uses / as the separator instead of spaces.
3. Verify locale/region inside the app
   • If the app has its own Locale or Region setting, ensure it is also set to English (United States). Different locales can expose different date formats and separators.

If the problem occurs in a specific Microsoft app (for example, Access or Project), adjust both the Windows regional settings and that app’s internal date format/locale settings so they are consistent.

References:

• Change the Windows regional settings to modify the appearance of some data types in Access databases.
• Regional settings and formats
• Change the date format in Project desktop
• Change how a date or time is displayed in a date picker, text box, or expression box
• The format change in the "Region and Language" dialog box does not affect the timesheet date in Microsoft Dynamics AX 2012