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For Outlook (follow Subscribe to a calendar steps): https://support.microsoft.com/en-us/topic/cff1429c-5af6-41ec-a5b4-74f2c278e98c
For Google (follow Use a link to add a public calendar steps): https://support.google.com/calendar/answer/37100?hl=en&co=GENIE.Platform%3DDesktop