Change date format on Planner (from US to Europe-LatinAmerica)

Hi Pedro, unfortunately the only way I have found to have Planner show the desired DD/MM is to use Planner in Teams and set the Teams language to English (UK).  It seems that some assumptions have been made in various M365 apps to just follow language as a way to decide date formats, rather than looking at the regional settings the user desires.  Not ideal I know.  Outside of Teams I couldn't get Planner to change from MM/DD and like you I see en-US in the initial Url, so I suspect this is driven by the organization setting.  Maybe it just takes some time.  To change the language in Teams, go to Settings (under the ... next to your profile picture in Teams) then Appearance and Accessibility and Language.  I chose to explicitly set it, as my M365 language was already English (United Kingdom).  In my testing I did see Teams detect this and offer to restart, but if you don't see this option after changing M365 Display Language to English (UK) then the explicit setting seems to force it.  I'd suggest giving feedback too, through the app, that the applications should follow regional settings.  You shouldn't have to put up with English UK spellings just to get the desired date format.

Best regards,

Brian