All I remember is that at the end people.come.from either the past or the future to watch everyone die.. what is this movie??

Sounds like The Time Shifters (http://www.imdb.com/title/tt0204686/) or possibly Timescape (http://www.imdb.com/title/tt0104362/)

Oooo! I think that time shifters movie is it! Ill have to check it out to be sure. Thank you!