Time travel has always fascinated the heck out of me. Funny enough the first concept of it was introduced to me through X-Men Days of Future Past storyline which was one of the first story arcs that introduced me to comics. Fast forward to the future (pun!) where that same story arc is going to now become a movie (yeeeah!) What was learned first and foremost since then is that any thought of slipping into any time stream results in what we like to call the possibility to 'create a tear into the very fabric of the time continuum!'. Better known as, if you change the past, it affects the future. A lesson that the group of friends in the trailer for this movie will be learning, you know, the hard way. The problem with time travel is if you continue to go back and forth changing things you may forget what everything was really supposed to be like in the first place. You may end up creating an alternate universe! Let's not go there. Again.