https://bugs.winehq.org/show_bug.cgi?id=46196
--- Comment #2 from João Ferreira devilj@outlook.pt --- (In reply to Nikolay Sivov from comment #1)
You can set it in registry in HKCU/Controls Panel/International/Geo, value name is Nation. We should probably set it on prefix creation to something sensible.
Many thanks, that fixed it :D
I would like to try to make a patch for it, so I'll leave this bug report open in the meantime.