iCal or ICS is a standardized format for storing calendar data including events and to-do-list. Apple Calendar is a personal calendar bundled with Apple Mail OS X.
Calendar files are saved in plain text format containing information such as title, summary, start time, end time for the event.
Primary File extensions
.ics file extension
Other file extensions
.vcal
How to Import calendars on Mac?
In Calendar app on Mac OS
Create a new calendar for the events
Choose File > Import
Select the files with the events
Click on Import
Choose the calendar to add events
You can also drag a file with events to the calendar.
How to export calendars from Mac?
Click on calendar name in the calendar list
Choose File > Export
Choose a location to save
Click Export
How to invite people to events in Calendar on Mac?
You can simply invite people to events using their names or email addresses. Follow the steps to invite people.
In the Calendar App on your Mac
Enter each invitee’s name or email address
If you see check availability below
Click Send