A permanent or sometimes only semi-permanent gateway that allows Time Travel but lacks the usual mobility of a Time Machine – the gateway's position in space is normally fixed – and the lightning-bolt arbitrariness of a Timeslip. Perhaps the best known sf example features in Robert A Heinlein's "By His Bootstraps" (October 1941 Astounding as by Anson MacDonald), where the device is explicitly termed a Time Gate and spans a modest Time Abyss of some 30,000 years. Further instances may be found in Charles L Harness's "The Araqnid Window" (December 1974 Amazing); in Christopher Priest's "Palely Loitering" (January 1979 F&SF), taking the form of bridges rather than gateways; and as "time-locks" in Diana Wynne Jones's A Tale of Time City (1987).
Media examples of note include the titular mechanism of The Time Tunnel (1966-1967); the original-series Star Trek segment "The City on the Edge of Forever" (6 April 1967), whose gateway is sentient and calls itself the Guardian of Forever; the temporal anomaly of Timeslip (1970-1971); the portal to 1876 in Kate & Leopold (2001); and the rift in both time and space that is central to Torchwood (2006-2011). [DRL]
see also: Star Ocean.