My online Outlook Calendar has reverted the old look and feel - why? Has anyone elses?

[nickcicc]

For the last 3-4 days, logging onto 365 to view my calendar has shown that the Calendar look and feel has reverted to the "old OWA style" calendar. I no longer see the new look calendar that has been in place for the last 6 months or so since Microsoft updated Outlook and Calendar online.

Has anyone else had this experience? Support are flailing and seem unable to restore the new look calendar for me.

[#2]

I have not seen there...what I have seen in some of my tenants is the use of the dark theme and I don't remember to have configured it