Finnish date formatting need correction
It's nice that O365 and Planner are localized into Finnish but unfortunately the dates have gone a bit wrong:
I can see dates like '31. toukota' which is meaningless for you can't add the partitive case ending (-ta) to the shortened form of the name of the month (touko). You could do that with the full name of the month (toukokuu --> toukokuuta), but best would be to use the short form of dd.mm.yyyy.