It's a few weeks now that I repeatedly find events similar to this in my calendar, everyday the same, forever:
- I don't know how it gets there
- I'd like to cancel it without notifying anyone (just to limit feedback to the guy)
has anyone got a clue?
Assuming this is a Google Calendar, the following advice from https://the-parallax.com/2018/05/11/how-to-stop-calendar-spam/ should help:
Google Calendar: From a Web browser, click on the event in Calendar, but be careful not to reply to it, and not to click on any of the links within it. At the top, under the Going section, click “Report spam.” The event, along with all others from that organizer, will be removed from your Calendar.
To prevent more spam from showing up on your Google Calendar in the future, click the Gear icon in the upper-right corner, and go to Settings. Scroll down to Event Settings, and change Automatically Add Invitations to, “No, only show invitations to which I have responded.”
There is no way to suppress sending notifications from the iPhone or macOS calendar apps. To do this you'll have to go to the Google Calendar web app (https://calendar.google.com), right-click the event, and click Delete.
I can't answer how the event got there, but if you've never declined or deleted it before, that would explain why you're still seeing it.