Adding an ICS calendar to your iOS device -- such as an iPad or iPhone -- is not done through the Calendar app. The settings to subscribe to ICS calendars are actually located in the Mail, Contacts, Calendars section of your device's Settings menu. You need the ICS calendar's full URL -- which is an ICS file -- to add it to the Calendar app. After you subscribe to the calendar, it appears under "Subscribed" in the Calendars section of the Calendar app.
Tap the "Settings" app on your iOS device's Home screen.
Select "Mail, Contacts, Calendars," then tap "Add Account" in the Accounts section.
Tap "Other," then tap "Add Subscribed Calendar."
Enter the ICS calendar's address in the "Server" field.
Tap "Next," then enter a name for the calendar in the Description field.
Tap "Save" to add the calendar to the Calendar app.
To change the name and color of the ICS calendar, open the Calendar app, and then tap "Calendars." Tap "Edit," then tap the ICS calendar. Select the new color, edit the name, and then tap "Done." Tap "Done" to save the changes, and then tap "Done" again to return to the Calendar.
It is also possible to subscribe to an ICS calendar on your iOS device by tapping a link to the calendar on a Web page, in a text message or an email.
Most major online calendar services -- such as Outlook.com Calendar and Yahoo Calendar -- have the option to export a calendar in the ICS format.
To stop viewing the ICS calendar, open the Calendar app, and then tap "Calendars." Tap the check mark next to the ICS calendar, then tap "Done."
To delete a subscribed calendar, tap "Settings," and then "Mail, Contact, Calendars." Tap "Subscribed Calendars" in the Accounts section, then select the subscribed calendar. Tap "Delete Account," then tap "Delete Account" again to confirm your choice.
Information in this article applies to an iOS device running iOS 7.1. Instructions may vary slightly or significantly with other versions and products.