When Does "World of Krypton" #1 v2 "Pieces" (1987) Take Place?

"World of Krypton" #1 v2 "Pieces" is a science fiction comic-book written by John Byrne and released August 11th, 1987. 

It takes place on an alternate timeline of the fictional DC Comics Universe in the year: 

99046 BC 

We know this because narration in "World of Krypton" #3 v2 tells us the events of issue #1 are a framed history “a thousand centuries past” while showing Jor-El (Kal-El/Superman’s father) watching hologram records of them. The plot continues into #4, but this part of the story only specifies one scene as taking place “months ago” so it seems likely that entire issue takes place within one year, the year Kal-El/Clark Kent/Superman is sent to Earth as a baby. 

"Man of Steel" #1 v1 (1986) and “World of Smallville” #2 (1988) establish that year as 1954 AD. 

A thousand centuries is: 

100 x 1,000 = 100,000 

so 

1954 - 100,000 = -98,046. 

And, in "World of Krypton" #2 v2, an omnipotent narration textbox tells us (from Van-L’s point-of-view), “Even after a thousand years…” while referring to something that happens halfway through that issue– in a scene that takes place on the same day as this issue. 

-98,046 - 1,000 = -99,046. 

Later, in "World of Krypton" #3 v2, the events of issue #1 are also referred to by an A.I. as occurring “in the year 10⁵/892 of the Fifth Age”. Presumably, 10⁵/892 of the Fifth Age is the equivalent year on a Kryptonian calendar. 

This comic-book was retroactively collected into a "Superman: The World of Krypton" paperback and then collected again into a later, expanded "Superman: The Many Worlds of Krypton" paperback. 

It is the chronologically earliest comic in the DC Comics Universe multiverse timeline (a chronological first comic to feature Kryptonians).