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 commentAnonymous commented
Agree with other comment. Setting the language to English-Australian in Teams fixes Planner within a Teams tab, but when you launch out to a browser it defaults to en-US and the date format is therefore back to US.