I just finished re-reading "Thief of Time," which I believe is the only Pratchett novel that is also a valid classpect... The various Time powers explored in the book aren't quite your average time-travel. The history Monks and the Thief himself can "slice," or speed their own time up massively, enabling them to move extremely quickly. (Which is similar to Wayne's speed bubbles in the Mistborn books.) The prayer wheels in the monastery can be used to manipulate the flow of time across space and history, and have been used to stitch the timeline back together after it got badly broken. The closest thing to Dave's "stable time loops" is the Yeti, who have the ability to reset themselves to an earlier point in their lives if they get killed.