I am not sure time is ever fated, but time is definitely manipulated in The Night Circus. It is a very interesting manipulation too. Celia and Marco are in a battle with one another. The battle ends when one of them dies. However, death by old age is not possible. The Night Circus is the "battleground" for their battle, and anybody associated with the Night Circus is a part of the battleground. The venue itself depends on the fate of Celia and Marco. The circus will remain unchanged so long as they remain. This does something very odd with time. Time passes at a completely normal rate for everyone involved. People inside the circus and outside the circus still feel the passage of time. However, the members of the circus do not age (or age incredibly slowly). Time has been halted for them in this regard. However, Poppet and Widget do (for some reason) age normally even though they are circus performers. As a thematic element, time is related to the book's love story. Celia and Marco are supposed to destroy each other. However, they end up falling in love. In order to save themselves and the circus, they have to find a way to exist outside of the circus without killing each other or anybody in the circus. This is why Bailey plays such an important role. The circus will presumably continue forever because it is ultimately rebound to Bailey and his life, and Celia and Marco are now able to actually live happily together forever.