Why is a calendar entry made for each call? I use a Samsung Galaxy Note.  I am noticing that each time I make, receive or miss a call, an entry is made in My Calendar, with the details of the call, incoming or outgoing, phone number etc.  Every call made / received in the phone log has one calendar entry, making the calendar totally unusable.

I am not able to find which application is doing this.  Is there any way I can stop this entry from being made for each call?

Alternatively, how do I identify which application is making this entry, by looking at the calendar entry?
The app SMS Backup+ has this functionality, where call log entries can be added automatically to a Google Calendar. The source code for SMS Backup+ is freely available on Github, so it may have been cloned and installed under a different name on your device.

Also if you go to your Google Account Permissions, you can see which apps have been authorized to access your Google calendars.