Author: Terry Pratchett
This book takes place on the fictional world of Discworld, which is a sort of planet shaped like a disc, resting on the backs of four elephants which are riding on the back of a giant space turtle, as shown:
(That's actually a cake, but you get the idea)
Throught the story it ranges all over Discworld, including the "outside of time" place where Death lives.
There is no specific time when this takes place, as the Discworld has different years than we have.