Dear KareyR5,
Thanks for using Microsoft products and posting in the community.
I understand that you have encountered an issue while changing the date and time of events in your calendar. This situation is indeed confusing and inconvenient, and now I will do my best to assist you. Let's try to solve this problem together:
Firstly, I noticed that you mentioned this is a new issue that you started encountering two weeks ago, and this is a new computer.
And starting in 2024, many new devices are preinstalled with new Outlook for Windows and don't ship with classic Outlook: You can't open classic Outlook on a new Windows PC - Microsoft Support
So, may I ask if you encountered this issue when switching to New Outlook two weeks ago?
Since you have Office 365, we recommend switching back to Classic Outlook to see if this issue still exists. If it doesn't exist, we speculate it's a problem with New Outlook. You can try uninstalling and reinstalling New Outlook to see the effect. If it doesn't work, we recommend using classic Outlook.
Tip: The new Outlook is a free email program released by Microsoft. It is not a paid Outlook obtained by Microsoft 365 subscribers. If you have ordered Microsoft 365 Personal or Home Edition. The Outlook you have obtained is the latest version of Outlook Classic. It has richer and more stable functions.
If this issue also exists in Classic Outlook, you can try creating a new configuration file and adding your account to see the effect: Create an Outlook profile - Microsoft Support
In addition to the methods in the link, you can also create a configuration file by following these steps:
Open "Control Panel" and select "Mail".
Click on "Show Profiles" and then "Add" to create a new profile.
Follow the instructions to set up a new email account and make it the default profile.
Hope this help you, please feel free to let me know how it goes. If there is any deviation in my understanding, please forgive me and provide me with more details. I am more than happy to continue to help you.
Best Regards,
Addie.C - MSFT | Microsoft Community Support Specialist