How many minutos does a movie need to be considered as one?

There are many animated shorts and filmes out there, but sometimes it´s just difficult to tell, if people would consider them as shorts or feature films.

The shortest animated movie could be Saludos Amigos, with only 42 min.

What do you guys think? I wanted to ask this, because i know a lot of beautiful animated works, but am not sure, if it would be okay to include them here^^