If you’re relying on an iOS device to manage your calendars, you may find that some eventually get duplicated and you’re dealing with a number of different calendars when you only need one.
There’s an easy way to edit them out. If you’re using the native calendar app, then just hit the “calendar” button on the top left-hand side of the screen and then choose the calendars you’d like to keep.
For other, third party apps, it’s going to be a little trickier and you can’t edit them from the Settings app.
To edit them out, you’re going to need to find the settings in each individual app, and then edit out your calendars there.