As an update, since we’ve still been seeing issues around date formatting, so we’re pursuing another fix that should help: If you’re using Planner within Teams, we will default to using the same language/local as Teams.
If you’re seeing this issue persist outside of Teams and your language/locale is set properly for your Office account, please let us know in the comments below!
The Planner Team
An error occurred while saving the commentJason Foster commented
All languages/region settings set to English (UK) (Office account, Windows login, MS Edge (Chromium)) but I still occasionally get the en-us page.
I find that the app switcher on O365 pages seems to be the culprit for me, sometimes the link for the Planner app contains en-us...
Also when creating new tasks it uses the US calendar format (Sunday as first day of week), this always happens regardless of anything else.