when should i start doing my hair and makeup?PLEASE HELP?

I have to leave for prom at 2. Im a total beginner and have never done hair or makeup, so ill need hour. But i dont want to do it too early so the hair falls out ut makeup fads, since ill need it all day and night. How long before i have to leave should I start doin it? Is 4 hours before enough, or earlier/ I dont want to stress out about being late, or have to leave with makeup bad