Tac Logis

On Imperial horology

2008-07-31T09:35:00.004+01:00

Third Week, Second Month: I don't know how the priest-emissaries of the Sky Father reckon time, but it doesn't fit the sun as it rises, nor the moons as they chase it. The Tax House of the Peculor Majoris is opens and closes at weird hours, sometimes it'll even close for 'nights' at Midday. And they seem to be getting real antsy about the new year, like it was just around the corner 'stead of more'n half a year away...

Since I'm aware there are some DH players and GMs who have little to no prior knowledge of 40k, and I didn't see the usual section in the core book explaining it, I thought I'd do the obligatory explanation of horology in the 41st millennium, and make sure people can figure out some of the weird dates.

A typical date might be 4.423815.m41. This can be broken down into 4 basic parts- 4. 423 815 m41.
The first part is the check number, which determines the degree of probable accuracy in the rest of the date:

a check number of 0 or 1 indicates the date refers to an event occurring in the Sol system
2 indicating a system in direct astropathic contact with Terra
3 indicates the source was not in direct contact with Terra, but was in contact with a class 2 source
In contact with a class 3, but not a class 0/1 or 2
In contact with a class 4 source
Was not in direct psychic contact with any other source at that time, but the date is part of a sequence that begins or ends with a source referenced date of class 1-5. The unreferenced period is no greater than 1 standard year
As class 6, but the unreferenced period is between 1 and 10 standard years
A check number of 8 indicates that the unsourced preiod is greater than 10 years
An approximated date- either this belongs to a date sequence with no fixed co-ordinate at either end (such as a date given from the Dark Age of Technology), or the date has been approximated from a non-imperial dating system

Obviously, check numbers of 0-5 are relatively accurate, while 6-8 represent a widening grey area of inaccuracy. Class 9 is somewhat different, but can generally be assumed to be roughly accurate (maybe). It is probably worth remembering that the period separating the check number from the rest of the date is optional.

The next portion of three digits (423 in this case) is the year fraction. Each year is broken up into 1000 equal segments, numbered 000-999, for administrative purposes (I suspect; and to my knowledge this is not stated in canonical fluff, but is fairly logical to assume; that these 'administrative purposes' are to make it easier to convert local dates, it being simpler to convert something in relation to 1000 than to 365).

Assuming an Imperial standard year is based upon a Terran sidereal year (not too unreasonable, imho) that gives us a year fraction (call it a 'Day') of just over 8hrs, 45 minutes and 57 seconds in length. Perhaps not unsurprisingly, this portion is not really in general use among Imperial citizens, although anyone who needs to refer to and keep track of time on different planets will do so in preference to local date systems.

Our example date is sometime between ~11:30 AM and ~8:15 PM on May 16th, therefore.

The next three digits are the year, going from 001 to 000 (one thousand), so our example date is the eight hundred and fifteenth of its millennium, which brings us neatly to the final portion of the date, which is the millennium itself. m41 (or occasionally M41, or just /41 or .41) is the forty first millennium, the 'current' period of the game setting, meaning our example date (which, like all general dates, may be abbreviated to the form 815.m41) is the 815th year of the 41st millennium (or the year 40,815 AD; or CE, depending on whether or not you prefer 'Year of our Lord' or 'Common Era').
Incidentally, this is the same year as the official setting for Dark Heresy.

So, if we put this all together, what do we get? 4.423815.m41= between 1130 and 2016 hrs on May 16th, in the year 40,815 AD, in a system that was in contact with a system in contact with a system in contact with Earth.

Now, there aren't any standardised weeks or months in the Imperial calendar (at least, not to my knowledge). Local cultures (ranging from a particular demographic/nation on one world to maybe even a whole sector, with the mode being a system) could very easily have a common definition of week and month, although the larger a particular local culture (or rather: the more widespread it is) the less such a thing will necessarily make sense.

That said, I'm tempted to (unofficially) define an Imperial standard week as ten Days and a month as 100 Days, which rather neatly gives us ten equal months of 36.5 Terran sidereal days, allows us to do neat shorthand regarding the week and month (3rd week, 4th month, 815.m41) and (if we shorten each month to 36 days, or 99 Days) we can have 5 intercalary days to play with, although that probably wouldn't work for the Imperial Day.

Local calendars will vary from the official Imperial calendar, but provided you know how long each day and year is compared to a Day and one Terran year, it doesn't particularly matter. Stuff can be swapped around as you want. Just stay consistent.

CF: Ophidian

2008-03-07T18:12:00.000Z

Vice-Admiral Tunguska stood upon the strategium deck of HDMS Atlantia, staring at the verisim actuality sphere that displayed his command. The warship contingent rode at high anchor above 43-Dobre, every one of them keeping perfect station on the Exorcist-class grand cruiser that was his flagship.

The auxilliaries and fleet support vessels were another matter. Half of them were still mustering from across the sector, and he'd been forced to detach Implacable to chase down stragglers and escort them here. In a way, the merchantmen that had arrived on schedule were even more of a headache: they wandered about the system without so much as a by-your-leave, cluttered up vox channels with inane chatter and insisted on sending small craft out between ships. He was certain that at least some of them were providing contraband to the naval crews, but short of ordering every shuttle blown out of the sky if it wasn't sanctioned by a command officer, there wasn't much he could do...

One of the things often forgotten in naval fiction, whether sci-fi, fantasy or historical, is the need for supply chains. In historical or fantasy settings, this is not so much of a problem, as there is virtually always going to be a coast nearby they can 'recquisition' food and water from, if not a friendly port from which to obtain munitions and other supplies. But in space, especially in 40k, with its manpower-intensive technology, things become more problematic. You need to consider keeping a force of millions (quite literally- even a light cruiser's complement can be on the order of 10,000 or so) in air clean enough to breathe, with enough food and water to tide them over until their next resupply. And that resupply could well be months, if not years away, thanks to the ...eccentricities of warp travel, combined with the exigencies of the service.
It can be alleviated somewhat by tithing the local infrastructure whenever you make planetfall, even if the tech base is too crude to support the other needs of the fleet, in much the same way that an age-of-sail captain might put in to a deserted cove to find water. However, that can only work to a certain degree- as air, food and water are not the only needs of a starship: spare parts, other consumable supplies (pots of paint, fabric for uniforms, tools, etc.), fuel, and of course munitions.
Yes, some would put munitions down as 'other consumable supplies', but when it comes to warships (whether mere escorts like frigates and destroyers, or full blown Ships-of-the-Wall such as cruisers and larger), I think it proper to give it a category all its own. After all, without anything to shoot, a warship is just a large, sturdy freighter with an inefficient and wasteful deck plan.

So, we have a general list of what a fleet of warships would need to remain operational, yes?
Actually, no: not quite, anyway. There is one other commodity that would need regular replenishment, and that is crew. Not officers, or even NCOs, necessarily, but crewmen.
An 18th century RN frigate (average complement around 200, officially), could expect to have one death aboard every six days or so, assuming no sickness swept among the crew, and the ship didn't see action. Given that 40k tends towards the grim and bleak, I suspect it is safe to say there would be a higher rate of death per hundred men or so. When you consider that the overall crew complement is much larger, I suspect that most ships (of cruiser size, anyway) see 20 or 30 deaths a week.
Of course, most of these would be amongst freshly pressed ratings: without the experience or training to know how to survive aboard ship, doing the thankless, ridiculously labour intensive and highly dangerous tasks, like scrubbing out and re-galvanizing the ship's central heating from inside the pipes; it isn't surprising they die off quickly, but they are easily replaced by another draft of slave-ratings.

So now we know a fleet needs food, water, fuel, air, spare parts, fresh crew, munitions and miscellaneous other consumables to keep going (those with too much time on their hands can work out which will be the biggest need). To get all of these, it needs a flotilla of fleet colliers to make the run back to the nearest supply depot (be it agri-world, hive-world manufactory or even or forge world) to pick up whatever supplies it is tasked with and then travelling to catch up with the fleet.

Obviously, those supply ships need to be either fast, lucky, or defended. Preferably all three.
Fast ships can make the run in very little time (obviously), reducing the risk of it being ambushed or simply lost. Defended ships (whether by convoy, or their own guns or by an assigned escort) have a chance at fighting off an ambush, but if they are escorted, that means more supplies are needed, so more supply runs, so more danger...

All in all, a neat little problem in logistics...