When you create a MS Team, it automatically creates a calendar. However, the calendar events are only available to members of your same tenant (.COM with .COM only, or .NET with .NET only). Although there are limitations in Teams, you can use the calendar you created in SharePoint by coping and pasting the calendar’s URL in Teams. If you prefer to use the calendar created in SharePoint as a tab in Teams, follow the instructions below.
Add a shared calendar in Microsoft Teams
1. Select a preferred channel in MS Team (i.e., General).
2. Select the + sign to add a tab
3. From the Add a tab window, choose Website.
4. Next, create a Tab name for the group calendar.
5. Next, copy and paste the group calendar URL in the URL section.
6. Click on the newly created Calendar tab of the channel.
7. Congratulations! You have successfully added a group calendar in a MS Teams channel.