Thread:Tupka217/@comment-24845073-20140726113351/@comment-43505-20140727114924

Secret Origins #6 gives June 26, 1924 as the date of the Wayne murders on Earth-Two. Bruce's headstone in America vs. the Justice Society #1 says 1915-1979. Helena Wayne was born in 1957, according to her headstone in The Last Days of the Justice Society special.

And in general, Earth-Two stories are assumed to take place several months before their publication dates as stated often by Roy Thomas in the 1980s in All-Star Squadron, Infinity, Inc. and related works.

A good source for Earth-Two Batman dates: The Golden Age Batman Chronology