From Carleton Moodle Docs
External calendars (such as Google Calendar, or a calendar from another Moodle site) can be imported into Moodle's calendar via the iCal standard.
To import a calendar via .ics file or URL,
- Add a calendar block to your page
- Click on the month to enter the calendar.
- At the bottom of the page, click the button 'Manage subscriptions'
- Give the calendar subscription a name and either enter a URL or upload an .ics file
- Click the Add button
A user who has permission to add course or group events, such as a teacher, can import a calendar and create course or group events.
Similarly, a user who has permission to add site events, such as an administrator, can import a calendar and create site events.
- Using Moodle how to have a 2 way sync with a Moodle and Google calendar forum post