By default the Calendar app on your iPhone or iPad will show calendars from the accounts you have added in the Accounts & Passwords section of the Settings app. However what if you want to add a shared calendar to your iOS device? The easiest way to do this is to install the Outlook app, which allows you to add shared calendars in a similar way to the desktop Outlook application. Adding a shared calendar into the default Calendar app is a bit more tedious, and is what we will explain how to do in this article.
Step One: Log into OWA (Outlook Web App) using the account whose calendar you wish to share
Step Two: Share the calendar via email
Note that this method will not work if you share to an email address within your O365 tenancy. Share to any email address outside your O365 tenancy, preferably one you have access to on your iOS device,
Step Three: Grab the .ics link
Do not select the “accept and view calendar” button in the email. The small link below the button is what we are after — you will need to copy that link to the clipboard.
Step Three: Add the calendar to your iOS device
Open the Settings app and go to Passwords & Accounts > Add Account > Other > Add Subscribed Calendar — in the “Server” field paste the link you copied from the email earlier and select “Done”.
Note that this method will only allow you to view the shared calendars — if you need to edit them using the default iOS Calendar app the only option would be to add the actual account sharing the calendar into the Settings on your iOS device. This would require the password for the account.