Unified Company Calendar for Mixed Microsoft 365 and Non-365 Users – 2025

You can consider this as publishing a shared calendar via ICS\HTML:

1. Create a Dedicated Shared Calendar

• Use Outlook desktop or Outlook on the web to create a new calendar (not a Group calendar).
• Name it something like “Company Events” or “Vacation Tracker.”

2. Delegate Editing Permissions

• In Outlook, right-click the calendar > Properties > Permissions.
• Grant Editor or Owner access only to selected M365 users.
• Set Default permission to “Reviewer” or “None” to prevent unintended edits.

3. Publish the Calendar to Web

• In Outlook on the web:
• Go to Settings > View all Outlook settings > Calendar > Shared calendars.
• Under Publish a calendar, select the calendar and choose:
• Can view all details (for full visibility)
• Get ICS link (for subscription)
• Get HTML link (for browser view)
• Share the ICS and/or HTML link with non-M365 users.

Please note, this method does not require recipients to have Microsoft accounts and works with most calendar apps such as Apple one