Microsoft Outlook Calendar for MacOS crashing: any event set to "All day"

Hi @Harry Lin, 

I hope you're doing well today. 

Thank you for providing the details about the issue in New Outlook for Mac, where the application closes whenever you create or edit a calendar event and change it to All day, while events with a specific time continue to work normally.  This issue may occur when Outlook for Mac encounters a stability problem related to how certain calendar item properties are processed, and Microsoft has also documented crash scenarios in Outlook for Mac that can be connected to calendar event data in specific builds.  In addition, if the local Outlook cache is not handling calendar synchronization correctly, specific calendar actions may trigger unexpected app behavior, which is why refreshing the local account data is an important troubleshooting step.  

Please follow the steps below, as they are the most suitable approach for your situation: 

1/ Refresh the Outlook account cache 

• In Outlook, go to Tools > Accounts. 
• Select the affected account, choose Manage, and then select Reset Account. Microsoft explains that this action refreshes the local cached data and allows Outlook to sync the affected items again. 
• Once the sync is complete, test creating or editing an All day event again.  

2/ Create a new Outlook profile and test again 

• Close Outlook completely. 
• Open Finder > Applications (If Applications isn't listed on the left side, click Go in the menu at the top of the screen > click Applications)

• Right click Microsoft Outlook, choose Show Package Contents, then go to Contents > SharedSupport > Outlook Profile Manager. Microsoft provides this method for creating and managing Outlook profiles on Mac. 
• Create a new profile, set it as the default profile, reopen Outlook, sign in to the account, and test the same calendar action again. 

• If you need a temporary workaround while testing, Microsoft also notes that you can use Outlook on the web. 
• Reference: Clear the cache in Outlook for Mac - Microsoft Support 

3/ Revert to Legacy Outlook, then switch back 

• If the issue persists, this step resets certain internal feature states within the New Outlook engine. 
• In the top menu bar, go to Help > Revert to Legacy Outlook. 
• Once in Legacy Outlook, briefly test an "All Day" event to confirm your calendar data is intact. 
• Go back to Help > New Outlook to re-enable the updated version and retest. 

4/ Contact in-app support  

• In New Outlook for Mac, go to Help > Contact Support.  
• This team has access to specialized diagnostic tools and deeper product insights, which can help investigate Outlook-specific behavior and provide more targeted guidance.    

As community moderators, we appreciate your understanding that our access to internal development details is limited. Our primary role is to guide users toward the appropriate resources and support channels. While we may not have visibility into deeper backend analysis, we’ll continue doing our best to support you within the scope of our responsibilities.          

I hope this information is helpful. Please follow these steps and let me know if it works for you. If you have any updates regarding the issue, please feel free to share them with me.           

Thank you for your patience and your understanding. I look forward to continuing the conversation.  

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