No, in my current project, we do not have a bug fix day. Personally, I am not a big fan of it, anyway. We work in 3-week-Sprints, so we can estimate our scope and put in a chunk of bugs (sorted by priority) as well. Then, we do soft zero-bug development, which means we try to do bugs first. That's not always possible, because there are too many bugs, and not all of them are all that relevant (like an API endpoint returning 200 instead of 204). So we fix the most important ones, then do features, and if there is time at the end of the Sprint, we do more bugs.