I've been having a nightmare with dates and spelling showing as US format. Here are my Windows settings:
and, here are my Office settings:
I wondered which sort of English that might be and so clicked on the “Add a Language” button to add “English (United Kingdom)”. This resulted in a changed display where “English” was replaced by “English (United Kingdom)”.
I think most systems will be set to “Match Microsoft Windows [English]”. In spite of saying it matches Microsoft Windows, it doesn’t actually match the UK bit of the Windows setting and, instead, uses US English!
Now that it reads “Match Microsoft Windows [English (United Kingdom)]”, I'm getting what I want.
How confusing is that?