Like all the other publishers, DC also published anthologies of weird stories (as opposed to continuing characters) in the 50s, but even before that, they had anthologies of adventure stories. The earliest time travel that I’ve found so far are from 1939: a two-part story of Slam Bradley and his sidekick traveling to the year two billion, A.D., in Detective Comics 23 and 24; and a five-part story, “A Playboy in King Arthur’s Court,” starting in in Adventure Comics 37. As for the 50s weird stories, the first one I found there was an H.L. Gold tale, “The Endless War,” in Strange Adventures 2. As I find others, I’ll list them in my time-travel comic books page.
History runs wild when Columbus, Napoléon, and Cleopatra journey through time from the past to the present!

Variants

(1)
  1. “DC Comics” by multiple writers and artists (1939).