Automatically delete old one off events
Thanks for being a customer and for reaching out! Take a look at Event Rocket, a third-party plugin that enables some additional features of The Events Calendar. This plugin should allow you to cleanup old events, as well as some other functionality.
Please keep in mind that this is not an official Modern Tribe plugin, and as such, we cannot provide support for it. If you have issues using Event Rocket, you can reach out on their support forums.
Just let me know if that answers your questions. Thanks! 🙂