Teams calender items not showing in windows 10 calender

6greens The account that you are logged into Teams with will be the calendar items are synced back with.  There are a few dependencies here,  one being the primary that the account needs to also have had it's Exchange mailbox moved into Exchange Online.  Assuming that is completed, then any meetings added to your Calendar in Teams - would show up in your Calendar wherever else you have it set to sync (Outlook / Windows Calendar / etc).  You may also want to check the calendar settings in the Calendar app to ensure items are downloaded as items arrive for the quickest view for synced items.  That can be found under the manage accounts section of settings in Mail.

/Josh