A Different Time *COMPLETED*

People in the present / future went back in time and established a city of advanced technology in the past. The future/present is then even more advanced in technology and they then take it back in time so the past city of the future gets more technologically advanced - and it keeps on going round in circles. People who live in the past know about the people who live in the present and vice versa. People called Time Postmen keep both cities connected through letters - whole relationships can be formed and family can keep in contact if they move cities. The rest on the world in the future know about the cities but for history's sake, the rest of the people in the past know nothing about the cities except for the citizens.