Open Calendar App
Tap hamburger icon to the top left of screen
Go to "Search" and view all events
To delete all scroll until it asks "Tap here to view events before xx/xx/20xx
Hold down on an event and mark all or the ones you want to delete
Tap delete and all events except Contact birthdays and Public Holidays will be cleared
On Galaxy Tab S7, I found the easiest thing to do was search for "e" as the most common letter. When search results come back, pick the first entry. An option for Select All then appears. Select that option and pick delete. If there are any remaining entries try other Wheel of Fortune letter (r,s,t,l,n) and eventually you get all events removed. I needed this to remove spam entries to induce a virus attack.