In the Dark Heresy time line, that is.
In Purge the Unclean, the dataslate with info on Ulbrexis and Morirr is dated 791.M41, and the text in the adventure refers to this as 14 years ago, which would put us around 805.M41. Yet some of the reports in the appendix are dated later, and refer to events in the past as late as 878.M41.
In The House of Dust and Ash, the Haarlock handout states Erasmus disappeared in 705.M41, and that this is more than a century ago.
Any other clues?