Q:

How long is a movie?

Is there a length of time in which a movie is not a movie?
Is there point where the movie is to long to be a movie? I am looking for some kind of time table in which movies are classified.

A:

It's somewhat a matter of opinion.  However, the Academy of Motion Picture Arts and Sciences defines a short movie as having a running time of 40 minutes or less (pdf).
By their definition a "full" feature length movie has to be more than 40 minutes.
I am not aware of any upper limit, there are movies such as Andy Warhol's Empire (1965) which is over 8 hours long and was shown in movie theaters. If that seems too much like an art installation rather than a feature film, there are a number of mainstream movies that are far longer than most made today:

Gone with the Wind (3hr 58 minutes)
Once Upon a Time in America (3hr 49 minutes)
Lawrence of Arabia (3hr 36 minutes)

