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

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

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

What do tu 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^^