Personally I don't think time exists because time is relative (think time dilation). I think time is really just our name for change. Most people picture time as a stretched out ribbon as in graphical timelines, but I think it's more like a solid point (just like there are many ways to graph information, there are many different ways people can graph time). The past is what happened in that point before it changed, and the future is simply what changes will take place. If there was something that never changed, then it would exist outside time. And there's no such thing as time travel; the measure of change is merely slowed or sped up depending on the point of observation.
Sorry if this doesn't make any sense. It sounded better in my head hahaha and I'm no scientist.