I’m a big fan of Microsoft Planner, and it’s a great way to intro people into using some of the extra Office 365 features that gives a pretty quick benefit with very little training.
However, this is one problem I’ve come across; there is no option to change the date format in Microsoft Planner. The date format itself is actually dependent on what language you’re viewing the page as.
Here’s two tasks created on the same plan in the same tenant:
All I changed was the URL. The URL format will be https://tasks.office.com/adamfowlerit.com/en-us/Home/Planner/#/… and the ‘en-us’ component can be changed to ‘en-au’ or ‘en-gb’ (along with other languages most likely that I didn’t test).
Depending how I access Planner seems to generate different a different language. There’s currently a uservoice request from a few years ago still being worked on, but at least you’re able to switch it over easily.
Hopefully we’ll see a default option available on each Planner itself. Until then, this is at least a fairly easy workaround which could take a while to discover for yourself.