40k date formats

By Seb, in Rogue Trader

Posted at

Although I am an avid 40k lore reader – read lots of novels, own most RPG material, I am confused about some 40k date formats. Maybe it is explained in the background to the original table top miniature game, but I must confess I don’t own any of that material and could not find any explanation in any of the RPG material released.


Most dates are indicated under the format [3 digits] M [2 digits], where I understand the last two digits indicate the millennium and the first 3 digits indicate the last 3 digits of the year. So that 814 M 41 for example refers to year 40814.


Where I get confused is that some date entries appear under the format [6 digits] M [2 digits]. The last 3 digits of the first six still seem to refer to the last 3 digits of the year. But the first 3 leave me clueless, as I have seen them range from 001 to 999, as in 001814 M 41 or 999814 M 41.


Does anybody know how to read this format? Days? Hours? Months? Many thanks in advance for any insight on this.

Posted at

Seb said:

Although I am an avid 40k lore reader – read lots of novels, own most RPG material, I am confused about some 40k date formats. Maybe it is explained in the background to the original table top miniature game, but I must confess I don’t own any of that material and could not find any explanation in any of the RPG material released.


Most dates are indicated under the format [3 digits] M [2 digits], where I understand the last two digits indicate the millennium and the first 3 digits indicate the last 3 digits of the year. So that 814 M 41 for example refers to year 40814.


Where I get confused is that some date entries appear under the format [6 digits] M [2 digits]. The last 3 digits of the first six still seem to refer to the last 3 digits of the year. But the first 3 leave me clueless, as I have seen them range from 001 to 999, as in 001814 M 41 or 999814 M 41.


Does anybody know how to read this format? Days? Hours? Months? Many thanks in advance for any insight on this.

Technically, it should be a 7-digit format (zxxxyyy.Mmm), rather than a 6-digit one, but a lot of people forget/ignore the first digit.

The first digit in that format is the Check Digit, used to define the accuracy of the date based on immediacy of Astropathic contact to Terra (a source on Terra is a 0 or 1, and the more uncertain the date is (and the more Astropathic relays needed to send the message from its origin to Terra), the higher the number, with 9 meaning that the date is only approximate (for example, if an event occurs on a ship in the Warp).

The next three digits are an arbitrary measure of time within the year, dubbed a Chronosegment in the 5th edition 40k Rulebook. Used primarily for Administratum purposes, they break a year up into 1000 segments, each a little over 8.5 hours in length.

The last three before the M are the year within the millennium, followed by the Millennium itself.

Posted at

Thank you very much to the both of you! Everything I wanted to know is there.

Posted at

N0-1_H3r3 said:

Technically, it should be a 7-digit format (zxxxyyy.Mmm), rather than a 6-digit one, but a lot of people forget/ignore the first digit.

The first digit in that format is the Check Digit, used to define the accuracy of the date based on immediacy of Astropathic contact to Terra (a source on Terra is a 0 or 1, and the more uncertain the date is (and the more Astropathic relays needed to send the message from its origin to Terra), the higher the number, with 9 meaning that the date is only approximate (for example, if an event occurs on a ship in the Warp).

The next three digits are an arbitrary measure of time within the year, dubbed a Chronosegment in the 5th edition 40k Rulebook. Used primarily for Administratum purposes, they break a year up into 1000 segments, each a little over 8.5 hours in length.

The last three before the M are the year within the millennium, followed by the Millennium itself.

Depends on how accurate the Ship's Log was on entering the Warp/how accurate a fix they can get on leaving: for most journeys an event that occurred in the Empyrean would be Check 6 (Uncertain, but part of a date sequence which begins and/or ends with a Class 5 Check Digit, with the unreferenced period being equal to or less than 1 year).

Check 9 would only come into play if a ship was out of contact with a class 0-5 source for over a century (which would be a really long time for them to be stuck in the Warp, or anywhere else, for that matter, though not unheard of), or if the event's occurrence (or the date thereof is conjectural- say as a result of archeological finds), or the date is a conversion from a non-Imperial calendar (xenos, local human or pre-Imperial human).

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Alasseo said:

Depends on how accurate the Ship's Log was on entering the Warp/how accurate a fix they can get on leaving: for most journeys an event that occurred in the Empyrean would be Check 6 (Uncertain, but part of a date sequence which begins and/or ends with a Class 5 Check Digit, with the unreferenced period being equal to or less than 1 year).

I imagine it depends quite a bit on the point of reference for the record - with time being essentially nonexistent in the Warp, events occurring within the Warp cannot have a defined date attached to them except by sequential approximation based on other available records. That is, an event occurring half way through a journey aboard a ship that enters the Warp in 5282811.M41 and reaches its destination on 5297811.M41 can be said to have taken place on 6289811.M41... but the event took place in the Warp, and consequently there isn't actually a guaranteed moment at which the event took place, only an approximation based on the subjective experiences of the crew.