If you noticed some spam events in your calendar, it is likely that the account connected to the app got affected (most probably, this is a Google account). You can follow the steps below to delete them:
- Open the Google Calendar web page.
- Log in with the same account, that is connected to the Calendars app.
- Check if you could delete the spam events from there.
If this is iCloud or any other account, please open the iPhone or iPad native Calendar app and try to delete the events from there.
Here are some related articles you may find useful:
- How to stop calendar spam (tips for Google, iCloud, and Outlook accounts);
- Make your Google account only show invitations to which you have responded;
- A Reddit thread, where people shared the methods that were useful for them.