I can now definitely confirm that the portion of the date for month, day, year that's pulled up in Outlook comes from the Short Date setting for Windows.
After changing mine to use the format that they use, 05-Apr-17, as the example of, my Outlook date filed displays as: Fri 26-Mar-21 11:21 AM
Now, mind you, that changes the display of short dates everywhere. My system clock shows 1:24 PM with the date beneath it being 26-Mar-21 now.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
To think is to differ.