Time travel is one of the hardest types of campaigns to run.
Time travel campaigns are also some of the most fun campaigns to run. Imagine traveling back in time to meet George Washington, Julius Caesar, William Shakespeare, Dr Martin Luther King Jr., and countless other influential people from throughout history. Imagine going back to witness the discovery of the New World, the signing of the Declaration of Independence, the birth of Christ, the splitting of the atom, the extinction of the dinosaurs, and countless other events which changed the world. Imagine changing history, JFK lives through the assassination attempt, Russia beats America to the Moon, the South wins the Civil War, the Roman Empire never rises to begin with, the Dark Ages never happened, ushering in an age of glory and knowledge which lasts thousands of years, and many other elsewhens to create, prevent, or explore. If you decide Time travel is just a way for tourists to get their kicks, then history cannot be changed, and anything done in the past has no effect, or was meant to happen to begin with.