Teams and Outlook Calendars

Hi RWAtechhelp, 

The new calendar app in Microsoft Teams is currently in the preview phase. This new calendar feature allows multiple shared calendars to be displayed in Microsoft Teams, similar to how it works in Outlook. The new calendar view offers optimized scheduling, customizable calendar views, and the ability to display different calendars simultaneously, enabling seamless coordination and event planning.
To enable the new calendar in Teams, you must first have the Teams Preview Policy enabled. Once this is set up, select Calendar in Teams and toggle the switch for the new calendar at the top right.

https://support.microsoft.com/en-us/office/get-started-with-the-new-calendar-in-microsoft-teams-98f3b637-5da2-43e2-91b3-f312ab3e4dc5

https://www.microsoft.com/microsoft-365/roadmap?filters=&searchterms=415415

https://appsource.microsoft.com/en-us/product/office/WA200006721?tab=Overview where you can track all PTO, vacations, holidays, and everyone's events from MS Teams, Outlook, Google and other external calendars in one place.

https://www.marksgroup.net/blog/microsoft-teams-add-a-group-calendar-to-teams/

https://www.marksgroup.net/blog/microsoft-teams-add-a-group-calendar-to-teams/ 

Hi RWAtechhelp,

there are two ways to add a shared Outlook calendar to Microsoft Teams (for that you need to have a Team and a channel created for all users):

Using the Channel Calendar app

1. Go to the Teams channel where you want to add the calendar.
2. Click the + button at the top of the channel to add a new tab.
3. Select Apps and then search for "Channel Calendar."
4. Click the Add button to add the app to the channel.
5. In the Channel Calendar app, click the Add calendar button.
6. Select From directory and then select the shared Outlook calendar that you want to add.
7. Click Add.

Using a website tab

1. Go to the Teams channel where you want to add the calendar.
2. Click the + button at the top of the channel to add a new tab.
3. Select Website as the tab type.
4. Enter a name for the tab, such as "Events Calendar," and paste the URL for your organization's shared calendar into the URL field.
5. Click Save.

To find the URL for your shared Outlook calendar, follow these steps:

1. Open Outlook and go to the Calendar view.
2. Right-click on the shared calendar that you want to add to Teams.
3. Select Share and then Calendar Permissions.
4. Click the Copy link button and paste the link into the URL field in Teams.

You can take a look at this article reagrding your issue:
How to add shared calendar to Microsoft Teams channel :calendar: - Microsoft Community Hub