In 2055, time travel was something that was a normal everyday thing. At Time Safari, INC. they took only the richest people back 60 million years ago.
After they shoot the dinosaur, Travis is mad at Eckel so he makes him walk back over to the dinosaur and take out the bullets because they can't be left in the past. Then they get back in the time machine and Travis says he might still kill him.
It is right here when Eckels notices that he had stepped on a butterfly when he stepped off the path. The whole future changed. The writing was different and the different president.