It can be because of the Google calendar setting to automatically add events from your emails. Therefore, if you receive confirmation emails with booking details, Google automatically adds them to your calendar. To turn off this option: click Settings icon in the top right corner of Google calendar//Settings//Automatically add invitations to my calendar//No. | It can be because of the Google calendar setting to automatically add events from your emails. Therefore, if you receive confirmation emails with booking details, Google automatically adds them to your calendar. To turn off this option: click Settings icon in the top right corner of Google calendar//Settings//Automatically add invitations to my calendar//No. |