Time travel is increasingly regarded as a menace. History is being polluted. The Encyclopedia Galactica has much to say on the theory and practice of time travel, most of which is incomprehensible to anyone who hasn't spent at least four lifetimes studying advanced hypermathematics, and since it was impossible to do this before time travel was invented, there is a certain amount of confusion as to how the idea was arrived at in the first place. One rationalization of this problem states that time travel was, by its very nature, discovered simultaneously at all periods of history, but this is clearly bunk. The trouble is that a lot of history is now quite clearly bunk as well.
The Campaign for Real Time was founded to prevent mucking up of the timestream. It was instigated by the incident wherein the Songs of the Long Land, poems of the famous poet Lallafa, were perceived to lose their value thanks to the meddling of time travelers. Though mocked at first - preserving time hadn't been fashionable since the outrage over aorist rods - it gained credibility when the Cathedral of Chalesm ceased to exist a few weeks later. Indeed, it is plain that a lot of history is now gone forever. The Campaign for Real Timers claim that just as easy travel eroded the differences between one country and another, and between one world and another, so time travel is now eroding the differences between one age and another. "The past," they say, "is now truly like a foreign country. They do things exactly the same there."