Mr. Laser Beam wrote:
^ It could be, but I doubt it. Weren't the opening credits of 'In a Mirror, Darkly' implying that the divergence occurred during, or roughly equivalent to, World War I?
The credits were fun but since they contradicted my personal canon, I wrote them off almost immediately.
However, it did imply a timeline divergence (well before WWI since there were sailing ships and even some kind of primitive raft) so it supports the overall idea of branching realities.
Besides, if the altered reality in "City..." was the Mirror timeline, then wouldn't Kirk and crew have detected the ISS Enterprise in orbit? There was NOTHING up there when they came back through the Guardian.
The ISS Enterprise
was in another part of the galaxy at the time, oppressing some innocent alien world for fun and profit.
Mirror Universe credits - if I wanted to be picky, I could point out that the Terran Empire logo doesn't show up till the WWII footage.