What time zone do you wan to change?
We have tried to change time zone in OWA, the machine and Outlook app
Do you want to change the time zone for your Office 365 account? About OWA, did you change it follow this article:
If this configuration is automatically rolled back, you could open a service request to let Office 365 team to help you change from the back end.
After changing time zone, you also need to change the configuration to apply this one to your calendar:
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