Outlook calendar entries spreading over 2 days

Hello Bubble, 

Thank you for reaching out! I can certainly see how frustrating it is to have your calendar entries shifting around, especially when you’ve already taken the time to reset them manually. 

To help me investigate this further, could you please let me know has the solution provided by Q&A Assist resolved your issue?

In the meantime, since this started around April 1st, it is highly likely that a recent Daylight Saving Time (DST) transition threw one of your settings out of sync by a single hour. This often pushes "midnight" into the adjacent day, causing all-day events to spread across two dates. 

Please try these steps to get everything back in alignment: 

Step 1: Verify the Mac's System Time Zone 

1. Open System Settings (click the Apple logo in the top left corner) and go to General > Date & Time. 
2. Ensure that "Set time zone automatically using your current location" is toggled On, and verify that the correct city/time zone is currently displaying. 

Step 2: Align the Outlook for Mac Preferences 

1. Open the Outlook app. 
2. In the top menu bar, click Outlook > Settings (or Preferences) > Calendar. 
3. Under the Time Zones section, ensure the primary time zone matches the one displayed in your Mac System Settings. 

Step 3: Align the Web Server 

1. Log into your email account via a web browser. 
2. Click the Gear icon (Settings) in the top right corner > Calendar > View > Time zones. 
3. Verify that the time zone here matches both your Mac and the desktop app. If it does not, change it to match and save the settings. 

I truly hope these steps work for you and gets your calendar back to normal. I look forward to your feedback and any updates you may share.

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This behavior matches a known issue with all-day events on shared calendars where events unexpectedly extend or shift because of time zone handling.

When an all-day event is created or edited, Outlook may treat it as if it were in UTC instead of the local time zone. In UTC-minus time zones, this can make a single-day all-day event appear to span two days.

Workarounds based on the documented issue:

1. If using a shared calendar where someone else has Editor permissions and edits the event, ask them to stop editing those all-day events directly on the calendar surface (for example, by dragging to extend). Instead, open the event and edit it in the item window.
2. If the calendar is shared and using the Shared Calendar improvements feature, disable the Shared Calendar improvements for the affected account as described in the article "How to enable and disable the Outlook calendar sharing updates" referenced in the known-issues documentation.
3. After disabling the Shared Calendar improvements, recreate one of the problematic all-day events and confirm it now stays on a single day.

If the problem persists only on specific shared calendars, verify whether those calendars are using the updated sharing model and adjust that setting per the same guidance.

References:

• Extending an all-day event on a shared calendar unexpectedly shortens or lengthens the event
• Known issues with classic Outlook Desktop Shared Calendar Improvements
• Create an all-day event
• Change an appointment, meeting, or event in Outlook