Re:John Carmack and John Romero reunited to talk DOOM on its...
by Fluorescence on Monday December 11, 2023 @08:38AM
(#38600516)
Wikipedia says 1 year: official team development started Nov 1992 and the first episode was released Dec 1993. IMHO this is underplaying it given Carmack started on the engine before that and it evolved from Wolfenstein 3D.
https://en.wikipedia.org/wiki/Development_of_Doom