Good news: yes, you can! The easiest way to display multiple calendars, using only the Commons’ built-in calendar functions, is as follows:

• Copy one group’s calendar subscription link shown at the bottom of the “Subscribe” section on the group’s main “Calendar” page.

• Navigate to another group on the Commons that you have permission to edit.
• Click on the “Manage Calendars” button in the top-right corner of the page if you’re logged in as that group’s manager, then click the “Add Calendar” button.

• Fill in a basic title for the calendar and the calendar subscription link you copied earlier.
• Select a colour to associate with this calendar (which is helpful if your group subscribes to multiple calendars).

• Press “Submit.” Make sure that the “Last Fetched” value for the new calendar you’ve just added doesn’t say “Never”—in which case you simply have to hit the “Refresh” link to the right.

Notes:

• If you get an error message when trying to refresh a calendar, or if the new calendar’s events don’t show up, make sure that the first group’s calendar permissions setting is set to “Any HUB Visitor” on the “Edit Group” page. If it’s not, the Commons will respect the first group’s permissions settings and prevent the group’s calendars from being shared in this way.
• Also, for both group pages and project notes, you can embed multiple external calendars—e.g., Google, iCal—using Wiki code snippets (accessible via the WYSIWYG page editor for groups or note editor for projects)! In fact, you can easily embed a public Google calendar or even a private Google calendar (though these can only be seen by people that have been added to that specific calendar via Google’s settings; if you try to access a private calendar, you’ll likely see an error/access restricted message).
• When editing a page or note, you can copy and paste the following wiki snippet to embed an external calendar and (optionally) specify its width and height (in this case, 800x600 pixels):
  • Iframe(https://calendar.google.com/calendar/embed?src=123], 800, 600)
    • In this test example,  the URL has been copied from Google. Please note that you would need to update the sample URL above  (“https://calendar.google.com/calendar/embed?src=123”) to correspond to that of the calendar you would like to embed. See https://support.google.com/calendar/answer/41207?hl=en for instructions.

More documentation is also available in the “Customizing a Group's Calendar” section of HUBzero’s documentation: https://help.hubzero.org/documentation/22/users/groups/groupcustom.