Timecycle And Chronocycle

Poul Anderson's Manse Everard of the Time Patrol time travels on a timecycle, like a wheelless motorcycle, and preserves the past whereas Stanislaw Lem's Ijon Tichy of the Temporal Institute time travels on a chronocycle, like a wheelless bicycle, and adjusts the past.

Talking to his younger self, Tichy answers an unasked question. Arriving from the future, he skids a hundredth of a second. Because Earth moves a few feet in that time, Tichy collides with a bookcase instead of landing in the center of the room. (I always look out for new slants on time travel.)

I will read about Tichy's temporal voyages. However, since Lem's approach is frivolous, I do not expect to find much commonality between the Patrol and the Institute. (However, no stone unturned approach.)

Heinlein's Temporal Bureau completes causal circles in an immutable timeline.
Anderson's Patrol counteracts causality violations and completes causal circles in a mutable timeline.
Lem's Institute does the gods know what.