: Just remembered that they also mention "the incompetent [...] who lost
: the Ascendant Justice". So that means Truth and Tartarus' likely
: takes place after the destruction of Halo on Sept 23 because that's when
: the ship was captured, but oddly neither of them mention Halo's
: destruction, nor can it take place on Sept 14 just after Op: First Strike
: because that would mean the Ascendant hasn't been lost yet and oh no I've
: gone cross-eyed ...

The time travel mechanic has no apparent story reason for existing. As kind of convoluted and screwy as the idea of Cortana encountering a corrupted version of herself caused by her own future events is intriguing, it's mostly because there didn't seem to be much of a point for throwing everyone back in time (it's not even crucial to the Forerunner crystal macguffin). If Nylund were on Twitter or somewhere easily accessible I'd ask him why it was added. Maybe there were some plans that went awry or never materialized.