Alternative versions of Superman establish a new continuity for DC, affecting not only Superman, but all of the DC Comics characters. The versions of Superman from this time period are traditionally divided into three main periods. The first version of Superman began being published by DC Comics in 1938 appearing in "Action Comics" #1. To explain discrepancies in the aging of Superman across several decades, his earliest stories were retroactively portrayed as having taken place on an alternative world called Earth-Two. These stories take place from 1938 until the late 1950s, although the exact dividing line is unclear and some stories happened identically to
Superman (Earth-One) the first time Superboy was referenced in a Superman story. The Earth-One Superman's first appearance (in a flash-forward) in a Superboy story was in "Superboy" (volume 1) #1 (March–April 1949). This version of Superman remained in publication through 1986. After the 1985-86 miniseries "Crisis on Infinite Earths", the Earth-One Superman was written out of continuity with the 1986 John Byrne miniseries "The Man of Steel". However, the Earth-One Superman was given a send-off in the final, noncanonical-to-Earth-One "imaginary" story "Whatever Happened to the Man of Tomorrow?" in "Superman" (volume 1) #423 (September 1986) and "Action Comics" #583 (September 1986). "For