Strange Calendar entry on iPhone, cannot delete

The blue calendar was some sort of calendar in the Microsoft Exchange category, which is what we used where I used to work, but I think I’m still on their Exchange server. I deleted the blue calendar, and now the September 1 entry has turned red. This calendar is simply labeled “Calendar” in the Exchange category, and it too makes the app crash. I also have a blue calendar in the iCloud category called Work which doesn’t have any option to delete.

If I turn off all calendars and open them one at a time, to see in what calendars the mysterious entry appears, it is categorized under “Other”, with “US Holidays Subscribed”. That’s the only calendar in which this event appears. The strange thing is, this calendar is a purple calendar. But the event appears with a blue line as shown in the screenshot. If I tap on the mysterious event which is simply labeled “New Event”, it shows it’s in a red calendar called “Calendar” in the Exchange category. Then when I go back to the listing as shown in my screenshot above, the blue line is now red. But now if I go back into my calendars, turn on the ‘’Calendar” in the Exchange category, the entry doesn’t show.

This is absolutely the strangest behavior I’ve ever seen.

I am attaching a screenshot showing a different view. Notice the multi-colored pill-looking graphic which I assume indicates the entry is in 2 calendars. However, as stated in my other post, the entry only appears in one calendar, the “US Holidays Subscribed” calendar.

Any editing I try to do on the event causes the app to crash and close, and whatever I tried to edit doesn’t save. I hope I haven’t been hacked somehow, and my phone doesn’t crash and burn on Sept 1.

I went to Settings > Apps > Mail > Mail Accounts > Exchange, and I turned off Calendar. But the event appears in the calendar assigned to the iCloud category. See screenshot. The blue line has now turned brown to match the color of the iCloud calendar.

[Edited by Moderator]

The same accounts appear in Apps > Calendar. I appreciate your efforts here. Thanks much.

Deleted. Same behavior.

@IdrisSeabright, I deleted the Exchange account. No change in behavior. I don’t think this calendar entry is associated with the Exchange account. I appreciate your help.