Office 365 Calendar Sharing Guide - Purple Computing
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Apple Mac, iPhone or iPad Calendar Not Syncing

Office 365 Calendar Sharing Guide


Microsoft are overhauling their calendar sharing processes to enable considerably better synchronisation of calendars in Office 365 / Exchange Online. This is across the whole spectrum of Outlook platforms (Outlook Web Access, Mac, PC, iOS). Likewise, they are building in better calendar sharing functionality to the native iOS and Android apps. Take a look at our guide to Office 365 calendar sharing.


General Approach To Calendar Sharing

At the present time it would seem that the best starting point for all calendar setups is as follows:

  • Each ‘real person’ to use their primary Exchange calendar for as much of their calendar content as possible
  • Users should make use of the Private option for calendar events they don’t want to be visible to colleagues, who might otherwise have permission to see them
  • Users should always initiate the sharing of calendars using Outlook Web Access (OWA). This ensures that a successful sharing of a calendar also syncs to the invitee’s mobile (iOS, Android) devices
  • Outlook Web Access allows you to set organisation-wide visibility settings for your own calendar
  • Additionally, OWA allows you to use the so-called ‘new style’ of calendar sharing invite/acceptance. This causes those calendars to sync correctly to mobile devices without needing to know the credentials for the individual shared calendars
  • Users may set up sub-calendars, each of which have their own sharing preferences, but there are some caveats:
    • A sub-calendar may be useful if a user requires a permanently private calendar area, since it’s not shared at all by default
    • Be warned however that sub-calendars do not contribute to your ‘free/busy’ status so they are not suitable for storing events where a user needs to be shown as unavailable for other bookings
    • Sub-calendars are therefore best suited to generic calendar accounts, where the availability of a particular individual is not being recorded, but you might have the need to sub-divide your calendar into different categories


“Sharer”: The person who is sharing their calendar

“Sharee”: The person who has been granted access to the Sharer’s calendar

“Office 365”: The Microsoft platform which includes Exchange Online (email and calendar), Sharepoint and other subscription services

“Exchange Online”: The component of Office 365 where email, calendar and contact services are configured and managed

“Outlook Web Access (OWA)”: The web-based version of Outlook you access using your web browser, as opposed to the desktop or mobile app which would run on your Mac, PC or mobile device. Accessible at

Private Calendar Events

The behaviour of private events is as follows:

General Assumptions

  • You have been given access to a colleague’s calendar
  • An event has been marked private by the owner of the calendar

General Rules

  • If you exclusively set calendar sharing permissions using Outlook Web Access, it is impossible to choose a permission level which would reveal the content of a Private event to your Sharees
  • If a private event was added to the Sharer’s primary calendar, it will impact their availability in the same way as a non-private event

macOS Calendar


  • You have added the Sharer’s account in Calendar > Preferences > Accounts > [Exchange Account] > Delegation panel under “Accounts I can access”
  • This will cause the sharer’s calendar to appear under “Delegates” in the left hand column of Apple Calendar


  • An event marked as Private by the Sharer will be invisible in Apple Calendar; you as the Sharee will not see it
  • If the private event was added to the Sharer’s primary calendar, it will still impact their availability when using the Availability Checker in Apple Calendar, even though the event itself is invisible

macOS Outlook 2016


  • You have added the Sharer’s account by clicking Open Shared Calendar and searched / added the Sharer by name
  • This will cause the sharer’s calendar to appear under “Shared Calendars” in the left hand column of the Outlook calendar


  • An event marked as Private by the Sharer will show as “Private Appointment” when you have their calendar set to be visible

Outlook Web Access


  • If you have received and accepted a calendar sharing invitation that was sent originally from Outlook Web Access, that person’s calendar will appear under the “People” section of the OWA Calendar sidebar


  • An event marked as Private by the Sharer will show as “Private Appointment” when you have their calendar set to be visible

Organisation-Wide Office 365 Calendar Sharing

It’s possible to set organisation- or company-wide access permissions to your Primary calendar only (this does not work for sub-calendars).

By default, other users in your Office 365 account can only view your availability (free/busy status). This means they can invite you to an event and check in advance whether you are free or busy for the proposed time, but they cannot see precisely what you are doing.

Changing Your Preference

It is possible to change your global calendar sharing preference by:

  • Logging into Outlook Web Access > Calendar
  • Right-click your primary calendar > Sharing permissions
  • Set the drop-down box to your preferred company-wide sharing permissions
  • None of the available permissions levels will cause Private events to be revealed


  • When the setting has been changed, all users within your Office 365 tenant will have effectively had a permission change to your calendar, but they will not receive any notification emails
  • By contrast, when individual users have access to your calendar granted or revoked, they will get an email
  • If a Sharee has been granted access to your calendar via this global permission, and they want to view your calendar, they will need to add it manually

Granting or Revoking Calendar Access To Individual Users

It is recommended to use Outlook Web Access to grant or revoke sharing permissions for the best experience across all devices, even if you are ultimately planning to use desktop or mobile apps to interact with Exchange Online.

By using OWA to set permissions, you are using Microsoft’s ‘new method’ of sharing calendars. This has major advantages:

  • Instant data sync of shared calendars
  • Zero-configuration required for shared calendars to appear on iOS and Android

To grant permission for other users to access your primary or sub-calendars:

  • Log in to Outlook Web Access
  • Right-click the calendar you wish to share > Sharing permissions
  • Add or remove the user(s) and in each case, set their permission level according to your privacy preferences
  • Very important: The Sharee will need to accept your invitation ALSO USING Outlook Web Access
  • Occasionally you’ll get a “UPN” result showing in the user search box, do not use this. Instead be sure to run a
  • Directory Search and choose the user from the local user directory.

Once a sharing invitation has been sent by the Sharer using OWA, and accepted by the Sharee using OWA, that calendar can now be added to Outlook by the Sharee.

How the Sharee Should Add The Sharer’s Calendar

Outlook Web Access

  • The shared calendar will appear automatically under the People section of Outlook Web Access

macOS Outlook 2016

  • The Sharee will need to use the Open Shared Calendar button in the toolbar (Ribbon) at the top of the Outlook application window
  • Simply search for and select the Sharer whose calendar you have been granted access to

iOS and Android

  • If your Exchange account has been added to your iOS or Android device, the Sharer’s calendar will appear under your primary and sub-calendars in your device’s built-in (native) Calendar application
  • It’s very important, once again, that the sharing invitation and acceptance take place within Outlook Web Access otherwise the mobile device will not show the shared calendar automatically

Primary Calendar and Behaviour Of Sub-Calendars

There is sometimes confusion between how Apple Calendar and Outlook 2016 for Mac display the primary and sub-calendars.

What is the Primary Calendar?

This is always labelled “Calendar” in Exchange and the name cannot be changed.

Events in this primary Calendar are the only ones which contribute to your Availability status. Sub-calendars do not affect your availability, when colleagues are checking whether you are free or busy at a given time.

Sub-Calendars (And Colours)

In a nutshell, all systems support sub-calendars which can be assigned different colours.

However, Outlook systems also support categories, which behave a little like sub-calendars but are not the same. Events within a calendar can have a category, and each category is denoted by a specific colour.

The category colour will override the more general colour choice for the calendar or sub-calendar itself.

Outlook 2016 may crash if you attempt to assign a colour to a calendar which already contains a categorised event. It can’t seem to handle the override system, where the colour of the category overrides the colour of the calendar.

General Behaviour

  • Outlook Web Access
  • OWA also allows creation of sub-calendars using the + button alongside “Your calendars” in the calendar sidebar
  • Subcalendars can have their colours changed in OWA by right-clicking and choosing a colour
  • Event in Outlook can be given a colour category, this overrides any colour set on the calendar as a whole

Outlook 2016 for Mac

  • Outlook 2016 can be a little confusing because your primary calendar has a dropdown which reveals multiple ‘categories’. These are a means of colouring / categorising specific events and are not the same as sub-calendars
  • Categories, if used, will sync across the Exchange platform and will appear in all versions of Outlook
  • Sub-calendars, if required, are called “Folders” in Outlook Mac
  • To add a sub-calendar in Outlook 2016 for Mac, right-click your account header in the Calendar sidebar and choose New Folder

Apple Calendar

  • Regular users of Apple Calendar will be aware that you can create new sub-calendars within an account. This is also true of Exchange accounts, you simply use the File > New Calendar option, then choose your Exchange account as the location for the new sub-calendar
  • New sub-calendars have their own colour which can usually be edited to your liking
  • If you have assigned a category to an event, Apple Calendar completely ignores this and there is no record of it on the event. The colour of an event in Apple Calendar is dictated entirely by the colour of the calendar.


Our recommendation is to avoid the use of categories and speak to Purple if there is a perceived requirement for segmenting your calendar events in a logical manner. There is likely to be a better way of meeting your needs.

Generic Shared Calendars

Sometimes it is beneficial to have one or more calendars belonging to a generic entity or business department / business function. For example calendars which do not belong to a ‘real person’.

Such calendars are set up as a Shared Mailbox within Exchange Online and access can be controlled through a list of ‘allowed users’ via the admin portal.

Adding Generic Shared Calendars To Your Device

There are two methods.

Method One : Sharing

  • Log into Outlook Web Access using the login credentials for the shared mailbox
  • If you don’t have this information, an administrator can generate a login for the shared mailbox
  • Share access to the calendars using the same instructions above, see the headers:
  • Organisation-Wide Calendar Sharing
  • Granting or Revoking Calendar Access To Individual Users
  • If you want the shared calendar to appear on iOS and Android devices automatically, use the latter

Method Two : Adding The Account Directly

  • It is perfectly possible to add the shared mailbox as an account to your device, such that it sits alongside your primary Exchange account
  • To do this, add the Exchange account to your device in the usual manner (beyond the scope of this document), using the login credentials for the shared mailbox itself
  • If you don’t have this information, an administrator can generate a login for the shared mailbox

Viewing Your iCloud Calendar In Outlook

Many users will have calendar data in other applications or services, iCloud being a likely example.

Use these instructions if you wish to be able to see your iCloud calendar data (read-only) alongside your Exchange calendar.

We hope you have found our guide to Office 365 calendar sharing useful. If you would like to find out more please contact us.


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