When someone is gone, they have left the place where you are and are no longer there. When something is gone, it is no longer present or no longer exists. He's already been gone four hours! By morning the smoke will be all gone
If you say it is gone a particular time, you mean it is later than that time. It was just gone 7 o'clock this evening when I finished. = after, past. the past participle of go
not present; having left; "he's away right now"; "you must not allow a stranger into the house when your mother is away"; "everyone is gone now"; "the departed guests"