Between Outlook Calendar accounts and Google Calendar accounts this is not quite straightforward to achieve. Because different companies ;)
NB: This tutorial is using Outlook Online Version
1- Go to the Outlook Calendar > then go to Settings > select Calendar then Shared Calendars.
2- Scroll down to Publish a Calendar.
3- Select the calendar you want to publish, select "Can view all details" then press Publish.
4- You will then get the URL you want, second row ICS. Right click and select Copy
5- Go back to GCal for Google Calendar.
6- Go to Settings > Add Calendar > from URL.
7- Click "Add Calendar".
Repeat the same steps for all the calendars you want to see.
NB: Please note that this is subscribing, not syncing, which means that you cannot edit the Outlook calendar from within GCal for Google Calendar. Also, changes in Outlook may take up to 48 hours to show up in GCal for Google Calendar.
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