uchronian

From uchronia +‎ -an.

uchronian (comparative more uchronian, superlative most uchronian)

1. Pertaining to uchronia ("an idealized or fictional conception of a particular period of time, especially in the past").

   Synonym: uchronic

   • 1945, John Laird, The Device of Government: An Essay on Civil Polity, Cambridge, Cambridgeshire: Cambridge University Press, page 115:

     For a long time to come, at least, it is too dangerous an experiment to base on hope. Again they may say that it never could succeed unless in a uchronian Utopia 'above these ruinable skies'.

• Jesse Sheidlower, editor (2001–2024), “uchronian, adj.”, in Historical Dictionary of Science Fiction.