Purpose

Currently a first draft. If anybody knows of anything that supercedes this please let me know.

I was having a look at my 3rd Edition rulebook and came across an interesting piece of text that explained the way dates work in 40K. ‘The March of Time’ on page 269. I’ve essentially lifted this text from the book as a helpful guide to those newer to the ‘fluff’.

40K and The Passage of Time

The passage of time in the 40K Universe is recorded from the perspective of the Imperium. As such, recorded events are based on a Terran standard.

Here is an example of a date taken from Codex: Imperial Guard 5th Edition.

4 105 999 M41. Reports that a single Catachan Guardsman named Marbo was responsible for the complete
destruction of the Ork Gargant Gorkanought are dismissed as ‘improbable’ by Segmentum Command.

Notice that I have broken the date down into 4 distinct parts. Although the last two parts are closely related.

The Check Number

The first digit (4) is the check number. Check numbers range from 0 to 9. They represent various states of reliability in the reported date.

0/1 - Terran standard date. Referring to an even that happened within the Sol system.

2 - Direct. Source is in direct psychic contact with Terra when date reference was made.

3 – Indirect. The source is in direct psychic contact with a class 2 source but not Terra.

4 – Corroborated. The source is in direct psychic contact with a class 3 source, but not a class 0/1 or 2

5 – Sub-Corroborated. The source is in direct psychic contact with a corroborated source.

6 – Non-Reference 1 Terran Year. The source is not in psychic contact with a class 1 to 5 source when the reference is made. However, the date belongs to a sequence beginning or ending with a date which does have a class 1 to 5 source reference. The un-sourced time period is no greater than 1 Terran year.

7 – Non-referenced 10 Terran years. This is an un-sourced date in the same way as a class 6 date, but with an un-sourced period of 1 to 10 Terran years.

8 – Non-referenced more than 10 Terran years. This is an unsourced date as for 7, but for an unsourced sequence of more than 10 Terran years.

9 – An approximated date. A date with no fixed coordinates at either end of a sequence, or a date approximated from non-imperially date references. Prefixes 1 to 8 indicate gradually widening ‘grey areas’ surrounding the origins of a given item of data. Prefix 9 is slightly different in the sense that it applies to a specific world/system/location and doesn’t correlate with Terran dates.

Year Fraction Number

The next 3 digits (105) make up the year fraction number. The standard Terran year is divided into 1000 equal segments (000 to 999). Standard Terran years are still commonly recognised as 365 days, they are just divided this way for administrative purposes.

Assuming that the Thousandths of a year is literally a division of year into a thousand parts (rather than something more complex); 1 Standard Terran day is roughly 2.739 Thousandths, so if you wanted to check which month a certain date occurred on, just divide the year fraction number by 2.739. 105/2.739 = 38.335. This becomes day 38 for arguments sake. So the event occurs roughly midway through February by Terran standards.

Year and Millennium

The last 3 numbers (999) make up the year. The date ranges from 001 to 000 as to be expected, seeing that we are dealing with Millennia.
The 40k calendar operates in the same way as the calendar does today. However A.D. (Anno Domini) is replaced with M (Millennia).

So the event happens in the year 40 999.