Exchange Online shared calendars on mobile devices

Iron Contributor

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?

24 Replies

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


@Julia Foran can give more details.

best response confirmed by VI_Migration (Silver Contributor)

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!


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?

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!



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.

@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. 

Hi @Dean Gross, I don't work for Microsoft so I wouldn't have any details on that but they did show off some Cortana integration with the Outlook calendar at Ignite that sounds like what you are looking for.  Checkout this session.

The reminder  by Cortana is definitely helpful, but it does not block out the time on the calendar which is needed to help others know about our availability when sending meeting requests.

I would recommend requesting the feature on User Voice.  I have seen several requested features implemented as a result of user voice input.

Thanks, I have done that.

Hi @Dean Gross@Mike Tilson is correct - the best way to ensure this gets attention & priority is voting for it in UserVoice. It's definitely something we have heard requests for as we start to release the "time to leave" feature with Cortana, so please keep voting!

Shared calendars viewable on mobile devices is something we've wanted for a long time and are grateful it has finally been released.

It works really well in Outlook for iOS and Android. A number of users who use other calendar apps e.g. native Calendar app on iOS and MacOS have reported a key issue as follows:
User A has access to view all details of User B's calendar as a  shared calendars

User B receives a meeting request from User C (outside the org).

When User A views the details of the meeting in shared calendar of User B. User A also appears as an invitee!

is anyone else having this issue?

Hi @Philemon Burney


Yes - this is a known issue with the native iOS app. The native iOS calendar app always adds the current user into the attendee list even if the user is not actually on the attendee list. This issue is mentioned in the detailed support article (



Thanks for your speedy reply @Julia (I can't tag you). That makes sense now - your support is appreciated!

Hello All. I honestly do not believe this has really been answered. The original question that is. The question was about the Native iOS calendar app. The links and videos to me at least seem to all have to do with the Outlook app. We are seeing a similar situation where calendars are appearing on peoples phones and they have no clue how that calendar got there. And this seems to have been recent within the past few weeks.

Mike, do you really feel that your original question was fully answered?

Hi Arnold,


  • If you accept a new sharing invitation, the calendar will appear on all mobile apps.
  • If you open a shared calendar, the calendar will NOT appear on mobile apps.
  • Nothing changes with existing calendars -- if you opened a calendar previously that synced to mobile (before we disabled those changes), it will continue to syncing to mobile.


If you're seeing something else, please raise a support ticket for investigation.






The biggest concern is that nobody remembers opening up another calendar on their mobile device. Additionally in our case they are not shared calendars. They are other people's calendars. Often it is direct reports. What strange is that some cases, it looks like OK, this comes from the organization attributes in AD, the person with the extra calendars is listed as the manager in AD, other times that is not the case though. Now sometimes looks like well all of those additional calendars are people who have some mailbox permission or other to the person who is seeing the calendars mailbox in exchange, then in other cases that is not true either. So we do not have a concrete answer as to where did this come from and more importantly, how can we control it.


I did open up a support case. After days of troubleshooting I was literally redirected to this posting.

Hi Arnold.  I do feel as though my question was answered.


Many of our users have permissions set for the default user (everyone).  When the Microsoft calendar team first made the change for calendars to appear on mobile devices they assumed if you opened a calendar from Outlook on the desktop (maybe web too?) that you were "accepting" the calendar even if you only had permissions via the default user. What would happen is our users would "calendar surf" in Outlook and those calendars were showing up on their mobile devices (Apple Mail & Outlook mobile).  There is no fix that I am aware of to remove those from the admin side, the users would have to remove the calendars from the mobile devices but they should not reappear.  Microsoft has changed that behavior to a new sharing model where you have to explicitly share your calendar with someone for it to show up on their mobile device.  I spoke personally with Julia at Ignite in September to better understand this issue.  Hope this helps.