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) several DC characters continuously published throughout the 1950s, there isn't a clear dividing line between the Earth-One and Earth-Two versions of Superman. Several stories published before the mid-1950s took place on Earth-One, such as "Superman" (volume 1) #78 from September–October 1952, the first appearance of the adult Lana Lang in Superman comics. Also, any Superman stories published before the mid-1950s that featured or mentioned Superboy also took place exclusively on Earth-One, as the Earth-Two Superman, per the earliest Superman comics, never had a Superboy career. The Earth-One Superman's first appearance in comics was in "Superman" (volume 1) #46 (May 1947),