You can import an unlimited number of external calendar feeds into your existing calendar. The calendar feed must be a valid iCalendar (.ics) file. External calendars are synced every hour.

• Open the calendar dashboard.
• In the top left, click on the calendars options menu, in the drop down click the "Edit Calendar" option.
• Scroll down to the "Import external calendars" section and click the "Add external calendar" link.
• Enter / paste the URL to the external calendar. The file often ends with ".ics".
• Click the "Save" button.
• The calendar file is now being validated. If the calendar file is missing a time zone indication, you are asked to specify the time zone.