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Google / Outlook multiple calendars

  • 11 August 2020
  • 3 replies

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I would like to clarify the best practise for using the Google & Outlook calendar integrations.

I need to sync multiple calendars that belong to different people across both these platforms. I could have 100’s if not 1000s of calendars to sync with via webhooks from my application.

At first glance it looks like I need to create 1 google account and 1 outlook account and then share all the calendars that I wish to sync with those accounts (If I want to keep this simple and fully automatic)

Are there any other options for setting up this type of integration? Thanks








Best answer by PaulKortman 12 August 2020, 14:01

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@penfold45 Zapier is not the ideal tool in this case when you are trying to sync things in two directions. I typically recommend a tool like Piesync when people are trying to do two-way sync of data. However, Piesync does not cover calendar events. In your case, you might want to look into Syncgene. I’ve never used this tool before and I don’t know it’s full capabilities but it looks like it might be what you are looking for. 


If however you are doing a “single source of truth” like all changes will only be made within outlook, we just need those calendar events to show up within a google calendar then there are a couple of zaps you would need to set up for that:

  • New Event in outlook
  • Change to an event in outlook
  • Deletion/removal of an event in outlook

I or someone else here can explain those zaps if that’s what you are looking for.

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@PaulKortman Why would zapier not be a good tool for the 2 way sync? It appears to have all the triggers and events I am looking for. What details am I missing so far?



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@penfold45 essentially you can create a never-ending loop. 


If you update an event in outlook calendar Zapier triggers and updates the event in google calendar. 

Zapier then triggers that there was an update to the event in google calendar and updates the event in outlook calendar

Zapier then triggers that there was an update to the event in outlook calendar and updates the event in google calendar



You can avoid this loop in a number of ways, but it’s additional steps and additional work.  So it’d doable but it’s not ideal. I use Zapier to two-way sync often, but it can be very complicated, especially with calendar events. 


Option 1 for preventing loops: Add a last synced timestamp/keyword to the end of the description. Then add a filter within the zaps (in either direction) to say hey, if the last synced keyword is in this direction then I don’t need to sync it again. -- Problem here is often times the sync from one to the other will overwrite the keyword and you’ll need to have some logic in to determine, hey how long ago was the sync timestamp and if it was less than 1 minute don’t sync - yet then that will miss syncing the second change if someone makes two changes to a calendar event 30 seconds apart.


Option 2 for preventing loops: You could add a bunch of formatting steps to determine if the calendar events match up, if so then don’t make any changes… often times this fails because the two calendar systems give information in different formats, so html versus plain text, a carriage return marked as \n or \r\n or a timestamp given in different format/timezone etc. So there are a lot of formatting steps you need to take into consideration.


Trust me, I’ve been using Zapier to Sync two ticketing systems and I estimated a month to get it working, it’s been 4 months and we’re still fixing edge cases, there are over 45 formatting steps in each zap!