Oldtimers (Pern)
in Anne McCaffrey's Dragonriders of Pern series of science fiction novels, the Oldtimers are a group of dragonriders who are brought forward in time .
In the Dragonriders series, Pern is subject to periodic incursions of Thread, a voracious and deadly space-borne organism that devours any organic matter it touches. Defending the population from Threadfall are dragons who can breathe fire to singe the Thread from the sky.
In McCaffrey's first Pern novel, Dragonflight, the dragonriders of Pern are concerned that they are not sufficiently numerous to fight the imminently arriving Thread. In the novel's climax, Weyrwoman Lessa brings 1,800 dragons and their riders—plus support staff and equipment—forward in time 400 Turns (years), thereby ensuring a sufficiently large force to fight Thread.
In later books of the series, the appellation "Oldtimers" is given to those who came forward from the past.
Read more about Oldtimers (Pern): Rebellion and Exile