We are using the standard Koronus setting and history, found on Fantasy Flight Games website:
Epoch Koronus

Note: PDF reader required.

Timeline for the Dominion of Saint Mordeci

The problem with time: real time is not finite or defined as we expect. There is no “fixed point” of measurement for time (“what is the base for a second?”), and we have even set the most advanced atomic clocks off 9 degrees of an atomic rotation to avoid correcting the current time-keep system that we use today. The Warhammer 40K Imperium uses “metric time”, which was adopted by the French in 1832 to keep track of electric and magnetic metric movements and is not used by lay people, who commonly use the sexagsimal system from the Babylonians. Metric time is far more efficient, as reference have been made to the use in “The Simpsons,” and the 1927 French film Metropolis, allowing for 100 fractions of accounting instead of the 60-, 60- and 24-elements in a 365.2422 fractioned year.

A way to think about this is to transfer a Gregorian date to a Julian date used by astronomers, and then multiple that day by ~2.7379092558307882, or (1000/365.2422). So March 2, 40814 (Gregorian) is the 62 day of the year (Julian) times (1000/365.2422) = 169.75037386150888, or about the 170 date. Written as a Warhammer 40K Imperial date, it would be x170814.M41, in which x is the degrees of separation from Holy Terra, and would be more exact for time.

Warp travel is also not congruent to real space; as in days may or may not pass in the warp without passing in real space and that at times warp travel may take you “backwards”. Additionally, each fixed point in the galaxy would relate to the passage of time different then a neighboring point; a full planetary rotations will feel like one day while another day may pass at a different rotation rate in a different gravity field, but both have the same effect of only one day. Thus, the process of date keeping in Warhammer 40k becomes a grand problem that may never, never be fully understood until space travel is a reality.

I view “the warp” as time itself; a fourth dimensional mess that we way simplify to relate with each other.

Date # of Days (24 hour periods) Location, Activity and Effects
Actual Perceive
2.062.814M41 3 Meet-up at Port Wander
21 Refurbishing the Raptum
5 17 Journey to Footfall
14 Establish ops on Footfall
? 8 Journey to Dolorium
? Time at Dolorium
? 68 Journey to Orn
66 Time at Orn
? 24 Warp from Orn to Thule Fleet
30 Time at Thule Fleet (check-in w/ Mertech)
? 10 Warp from Thule to Footfall
10 Sale at Footfall
Total 271