Hi Kenn,
Thanks for reaching out!
There is not currently any built-in functionality to automatically redirect past events, but you could do it via a customization. Our themer’s guide is the place to start if you’d like to give this a shot! Our list of functions might also be helpful. I would take a look at tribe_is_past_event() and wp_redirect() as a staring point. If you would like to have the code done for you, we also have a list of recommended developers.
If this is a feature you would like to see added in the future, we’d love it if you could post the idea in our Feature Ideas Forum! We use it to gauge user interest in new features and help plan future development.
<i>However</i>, past events should not return 404s just because they have passed. By default, the only thing that really changes on the event page once the event has passed is that a notice appears indicating that the event is in the past (see this example from our demo site wpshindig.com). Are you using a plugin or another method to automatically remove past events or set them to draft status?