User blog comment:ImperialFist31/42nd Millenium/@comment-26233146-20150501121952

I'm assuming that DoWII is set in M42 based on the fact that the Tyranids in the original game are noted to be a splinter from the battle at Tarsis Ultra (which happened in 999M41) with Chaos Rising happening a year after that and Retribution happening ten years after Chaos Rising.

Similarly for the Priests of Mars series they reference things like the Ophidium Gulf incident and the battles of the 13th Black Crusade as happening in the past.