We consider it impolite, if you show up for an invitation at someone’s home before the time you were invited for. Many would say it is even impolite to show up less then 5 minutes late, and consider being 10-15 minutes late the best, and up to 30-45 minutes acceptable.
For a business appointment or doctor's appointment, where there is an assistant that opens the door and a waiting area, it's expected to be early, so that you are already in front of the correct room when the appointment starts.