The Uptime Gate was a powerful time corridor that connected the City of the Saved to the universe. In the City, it took the form of a block of stone about a mile high, situated in the Erstwhile Plaza in Central District. While open, it was the site of innumerable reunions, partings, pageants and expeditions, but it was eventually closed and sealed. (PROSE: Of the City of the Saved ...)

Technically the term only applied to the terminus inside the City, but it was generally used to refer to the other end as well. The in-universe end was situated on a mountain on a distant planet close to exactly on the frontier in time, so far from the War-time powers that the entire area almost existed in a state of truce. There was also the fact that no one wanted to risk provoking the City by fighting near/for it, of course. The area around the Uptime Gate became a posthuman settlement called Ascension. (PROSE: The Book of the War, Of the City of the Saved...)