Outlook calendar will not allow a date or time change to a scheduled event via the date/time pull downs

The "Scheduling Assistant" workaround was the only solution of the many in this thread that worked.

Per one of the suggestions, I un-checked the iCloud Add-in and then opened Classic Outlook in Safe Mode. I was then able to change appointment dates/times.

Re-checking this add-in resulted in not being able to change dates/times.

So for me (Windows 11, Microsoft 365), this add-in is the problem and Apple & Microsoft aren't working together correctly.

Which is very odd because up until a week or so ago, this wasn't an issue at all.

****MARCH 10, 2025 UPDATE****

After over 20 years of using Microsoft products, ***I will not be renewing my Microsoft 365 subscription.*** I'm tired of all the bugs, the lack of customer service, the confusing products with different passwords (Outlook, Outlook.com, Outlook Classic, Outlook New, Live.com, My Microsoft, Office, Microsoft Office, Your Microsoft Office, Office for the Criminally Insane, etc.) Tired of Outlook unable to sync IMAP folders, Outlook taking forever to look up AT&T's mail server, and, of course, the issue raised in this thread. (Not to mention that whenever there's a problem with Outlook, Microsoft tells you there's a corrupt file and you should create a New Profile ... a solution which has NEVER worked for me.)

So here's MY solution: I installed Thunderbird. It does everything Outlook does: reads email, stores your contacts, and provides a calendar for you to record tasks and appointments

Thunderbird's Calendar syncs with my Apple iPhone SE's Calendar. Here's how:

https://www.youtube.com/watch?v=hBXJKkMuXZ0

"Thunderbird is an open source app that lets you manage your messages, calendars, and contacts in one fast and secure place. It is funded by donations and respects your privacy and freedom."

IT'S FREE and it's brought to you by the same folks who bring you the Firefox internet browser. I've used Firefox (IT'S FREE) for several years and it's just as good as the Chrome browser ... which, of course, is a Google product. 'Nuff said.

As for Microsoft's Word, Excel, and PowerPoint programs, you can get the same type of applications with Libre Office: https://www.libreoffice.org/ It's open source, FREE, and you can say goodbye to Microsoft forever ... except for their Windows product.

I'm having exactly the same problem with Microsoft® Outlook® 2016 MSO (Version 2410 Build 16.0.18129.20100) 64-bit. Let me know if you need any further information from me.

The workaround is to use the Scheduling Assistant to change the date when making a new calendar entry

In my outlook calendar I can no longer change the date or time of any event using the pull down arrows to change the start date or time. When I input a new day or time, it reverts back to the original. I am able to change the date/time of event by dragging the event, but this is cumbersome. It is a new computer and Office 365. This is a new issue and started approximately 2 weeks ago.

Suffered the same issue and went nuts. Yet found the solution for me. Uninstalled MS 365 and iCloud. Then I specifically installed the 32bit version of MS 365 from my MS Online Account, not the proposed "standard version". Then reinstalled iCloud from Microsoft Store. And ... calender worked fine again. Miracles happen.

It's not just overlaps where this is happening to me - any meeting - either adding or modifying an existing one. Fortunately I use iCloud for my calendar so I can go to my phone and change the time on that.