A Microsoft Power Automate flow to synchronize two Outlook 365 calendars.
Download the zip archive from here.
If you want to get rid of all blocker events, you can use this helper PowerAuto flow.
Please see this blog post for details.
Note: there is also a fork of this flow that synchronizes your Outlook <-> Google calendar, see here.
Important
v0.9 introduces major changes to the synchronization core logic. The main new feature is that the location field is now synchronized. However, running multiple parallel flows (to synchronize more than two calendars) is no longer supported! Please carefully read the points below for more details.
v0.9 of the flow also consumes a few more actions than v0.8, thus you might reach your daily quota/limit more quickly. If you don't have a strong need to synchronize the location field (or if you want to synchronize more than two calendars), you should stay on v0.8 or older!
- WARNING: if you are upgrading from 0.8 or older, you must first run the Delete SyncBlocker events flow to delete all old SyncBlocker events (because they are incompatible with v0.9 and newer). You must run the Delete SyncBlocker events flow once, for every calendar that is affected by your v0.8 (or older) synchronization flow.
- Note: the zip archive of the Delete Syncblocker events flow has been updated, so that it can delete SyncBlocker events created with v0.9 or newer. Should you run into problems with v0.9 and want to revert to v0.8, make sure that you download the new version of the Delete SyncBlocker events flow (and re-import it into Power Automate), to properly clean your SyncBlocker events.
- Feature: The location field of your calendar events is now synchronized to the SyncBlocker events. In v0.8 and older, that location field of the SyncBlocker events was used to store the ID of the source event. In v0.9, that ID is now stored in a fake email address in the first required attendee of the SyncBlocker event. Make sure not to delete this attendee!
- Note: by default, whenever a Power Automate action creates a calendar event with attendees, the Outlook 365 platform automatically sends invitation emails to these attendees. The v0.9 flow uses email addresses such as
do-not-delete-this-attendee-or-sync-breaks@<sanitized-event-id>.invalid. Normally, sending emails to such non-existent addresses would fail, causing a "delivery failed notice" email to be placed in your inbox for every synchronized event, which would be extremely annoying. However, the<sanitized-event-id>is over 110 characters long, and the Outlook 365 platform (fortunately) skips sending invite emails to email addresses with such a long host name (for reasons we don't know). However, there is a chance that Microsoft changes this behavior, or that Outlook 365 behaves differently for your account/tenant. Consequently, if you get these failed delivery notice emails, you will need to revert to v0.8 of this flow.
- Note: by default, whenever a Power Automate action creates a calendar event with attendees, the Outlook 365 platform automatically sends invitation emails to these attendees. The v0.9 flow uses email addresses such as
- Feature: The setting "SyncBlocker prefix" is now optional, because the synchronization algorithm now disambiguates real events from SyncBlocker events via the required attendees field. If you want, you can now set the SyncBlocker prefix to an empty string, and instead use a category (configured with a custom color) to visually disambiguate your real vs. blocker events in Outlook. You may now also change the SyncBlocker prefix at any time, the flow will automatically update the subject/title of all events accordingly (in v0.8 and older, you were not allowed to change the prefix after running the first sync).
- Feature: For already-synchronized events, changes made to the title / subject of the source event are now propagated to the SyncBlocker event.
- Add support for (optional) uni-directional synchronization, by adding
two new settings named Synchronize from calendar X to calendar Y
which you can set to
falseas desired (default istrue) - Add new setting Synchronize events without other attendees (default is
true). Set this tofalseif you do not want to synchronize events that you created just for yourself (e.g. reminders for a doctor's appointment), i.e., events that have neither optional nor required attendees (other than yourself)
- Add new (optional) setting Category for SyncBlocker events in calendar 1/2 which you can set to an array of one or more Outlook category names, which are assigned to your SyncBlocker events. The updated categories will also be retroactively applied to already-existing SyncBlocker events
- Fix errors such as
InvalidTemplate. The execution of template action 'Cal1_SB_events_with_matching_location' failed [...] property 'iCalUId' doesn't exist [...]by filtering out events that do not have aiCalUIdproperty for some reason - Add new setting Hide event details in calendar 1/2. If you set this to
true, the sync blocker event will not have the real subject and body of the corresponding real calendar event, but a dummy text. This is useful for privacy reasons.
- Fix the displayed date of all-day events be distorted (see #2), by fixing the "all day" event attribute
- Fix the sensitivity event attribute, so that private events also appear as private for the blocker events
- Improve synchronization stability by using the unique CalDAV ID (instead of Outlook's internal event ID), and specifying an upper limit when querying for events. This should reduce any accidental duplicated blocker events.
- New setting: configure whether event reminders should be shown for blocker events
(on by default, set to trigger 15 minutes prior to the event start time). The
use case is to set this to
falseif you configured Outlook to show both calendars anyway
- Simplify the set up: now you only need to specify the calendar names (as shown in Outlook) - it is no longer necessary to change the calendar ID in each Outlook-related Power Automate action
- Synchronize the "showAs" field of the blocker events