Exchange Online shared calendars on mobile devices

Mike Tilson
Occasional Contributor

Exchange Online shared calendars on mobile devices

Earlier this week we had a few users start to notice other users' meetings showing up on their calendars on the native iOS calendar app and the Outlook for iOS app.  I experienced the issue as well.  When I opened the Outlook app I could see 3 of my colleagues events on my calendar that I was not part of.  I had recently looked at those calendars via Outlook on my PC.  Today I noticed that someone else had posted about the issue on Twitter.  The calendars are easy to remove and I am only aware of 1 instance where the calendars returned on the mobile device.  Does anyone have any details about a change that Microsoft would be rolling out that would have caused this?  Anyone else experience the issue?

6 Replies

Re: Exchange Online shared calendars on mobile devices

That would most likely be the new Calendar sharing model as detailed here:


@Julia Foran can give more details.


Re: Exchange Online shared calendars on mobile devices

Hi Mike,


This is part of the shared calendar improvements we are enabling & discussed during last year's Ignite conference that Vasil linked to. These improvements address a long-standing request from users to sync Office365 shared calendars to mobile phones (iOS UserVoice, Android UserVoice). We started slowly enabling this for users at the beginning of this year.


In the first iteration, newly accepted shared calendars would sync to mobile phone if the calendar was shared & accepted from Outlook on the web. In the next update, calendars could be shared from any Outlook client, and as long as the users accepted in Outlook on the web, the newly accepted shared calendar would sync to mobile.


However, it's possible to grant calendar permissions from Outlook on Windows or Mac without a sharing invitation being sent to the users. When we started releasing these improvements, many users pointed out that they "accept" shared calendars by opening the calendar in Outlook (rather than accepting a sharing invitation). So we implemented an experimental update that allowed a calendar to be accepted from Outlook on the web or Windows, using either the accept button or by opening the calendar.


This expermental update turned out to be the most noticeable difference for users like yourself. The feedback has mostly been that if I open a calendar for which I don't have direct permissions (e.g. viewing a calendar of someone in your organization with the default user permissions), then we shouldn't sync those calendars to mobile phones. However, users did want calendars to sync to mobile phones if they're opened a calendar for which they've been granted individual permissions.


To support that user feedback, we have temporarily disabled the "open calendar" update, and we're working on adding a check to determine if the user who is opening the calendar has individual permissions to the calendar. So, the current state is that only calendars accepted in Outlook on the web from a sharing invitation will sync to mobile. (However, soon Outlook on iOS and Android will also support accepting invites!)


This should hopefully explain why you see some of your colleagues' calendars on your mobile phone - if you opened a calendar in the past week or two, it was considered "accepting" the calendar and it started sync'ing to mobile phones. You can use Outlook on the web, iOS, or Android to delete the calendar, and at this point, the calendars won't re-appear even if you re-open them from Outlook.


Hope that helps explain the issue you noticed!


Re: Exchange Online shared calendars on mobile devices

Thank you @Julia Foran for the quick and detailed response.  I would like to be proactive with our internal support personnel when these new features are pushed to our tenant.  Is there a reason this was not posted in our tenant admin message center?


Re: Exchange Online shared calendars on mobile devices

Hi Mike,


That was my fault, and I truly apologize that you weren't notified in advance of a change that you considered a functional difference.


The reason I did not post to the Admin Message Center for this update is because it was considered a bug-level fix to align the same action (add calendar) to have the same behavior (show in mobile). Since early 2017, clicking Accept on a sharing invitation showed the calendar in mobile, and Accept & Open are supposed to be equivalent ways to add calendars, so we were fixing this inconsistency.


You'll notice that a key theme for Calendar team this year is consistency, and we are doing our best to ensure that the same actions always result in the same behavior, even if they are initiated in different ways. An equivalent example of a bug we'll also be fixing in the future is that a newly added shared calendar should go into the same calendar group no matter which client you accept from.


In the case of updating "Open calendar" to match "Accept calendar", as soon as we started hearing feedback from admins that they wished to have notified about this, we immediately disabled the update and will not re-enable until we do an official communication through the Admin Center as requested. Also, as mentioned earlier, we will probably only re-enable it for opening a calendar shared directly to you which is more equivalent to the Accept path.


On a related note, one thing that has already been planned as a communication through the Admin Message Center is an upcoming post about delegated calendars on mobile. We're about to start rolling out support for delegated calendars to sync to mobile phones when the user accepts an invite. The Admin Message Center post will link to this support article as a guide about all the shared calendar improvements. I'm sharing here early since we're on the topic of shared calendars & communications.


Thank you for sharing feedback on this issue, so that we can improve. I'm taking this to heart, and I'll work on sending communication even for small changes in the future. Also, if you have any feedback on the support article, feel free to message me directly here on TechCommunity!



Re: Exchange Online shared calendars on mobile devices

Thank you again for the quick reply and detail.  I am impressed by the response I have received.  I look forward to hearing more from you next week at Ignite.

Re: Exchange Online shared calendars on mobile devices

@Mike Tilsonthanks for the presentation, it was informative and it reminded me of a long standing issue: accounting for Travel time to meetings in other buildings, i.e., if we have to go to a meeting, we are not available and the calendar should reflect this time to others. Is any work being done to improve Outlooks ability to handle this?

It should be rather straight forward to provide the ability to add time before and after a meetings start and end time to account for attendees individual travel durations. 

People have been asking for this for years, but it has never been implemented and we have been forced to add separate entries to our calendars to block out the travel time. 

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