Events in Calendar have disappeared

When I opened the Calendar app on my iPhone 14 today I realised with terror that all the calendars that I have created over the years have disappeared (they are not hidden) and that all the events I have created in my calendar (past and future) have all gone.

As I have never archived calendars, they cannot be restored from iCloud.

I have also never synced calendars with my laptop so there's no trace there either.

Any idea on how to fix this will be very welcome. Thank you!