This is actually a bigger deal than the post indicates, and because you can’t edit an override, and because there is no ability to create an override that is in the past, there isn’t a way to really even change an override once its started without losing the history.
So to repeat if you need to edit an override once its started, you lose the past history of who took on-call when for that override period. If someone comes back from vacation a couple days early, you have a choice to keep the history of who volunteered to take the on call for that person, or keep the person who took on call for that person on call to not lose the history. That’s not fair.
I’d like to vote to bump the priority higher on the ability to edit an override schedule.