For purposes of converting the rules for a Black Crusade in Tome of Plague to other rule systems, I'm wondering how long a Crusade Turn should be considered. Does anyone have any idea of about how long it should be considered?

There are some events that take place every 30 days or every 90 days or so in some of the game systems, and knowing this will be important.

I think it's left very abstract on purpose as everyone's mind will conjure a different amount of time per turn naturally.

Considering that each turn comprises of massive forces clashing over numerous planets and transports taking combatants over vast distances I view each game turn as something akin to a year or even longer. After all if the period is too short it can be said you conquered an entire sector (or at least the big, important bits) in possibly just a couple of years or sooner.

That being said just use what you think should be an appropriate amount of time when you convert the black crusade rules to your other systems. Like so many other things, there are no right or wrong answers, just what feels best for your particular group.

Additionally, since you're travelling through the warp to reach each location, does it really matter? Chances are you'll arrive in sync with everyone else or three weeks before you started while your other self is already fighting next weeks battle!

It is very open though, imagine how long it might take to win a battle, it could easily take days, weeks, months just to make any progress. Now envision that scaled up to the conquest of an entire planet where you could easily spend say six months to a year just bogged down in one location trying to corrupt it.

Primarily for purposes of colonies in Rogue Trader, I'm going to say each one is three months, or 90 days, with a clause that one can increase or decrease this number if they feel it is appropriate. Also, I'm expanding these rules rather heavily so that any kind of endeavor can be undertaken and one can have one's competition in the fray as well--whether this be rival rogue traders or other xenos races.

An interesting idea, I was pondering the other day if the Black Crusade rules might be useful for a militaristic Rogue Trader campaign.

Heck you could even have a sector fall to your group of heretics in a Black Crusade Campaign and then be part of a coalition trying to take it back in a counter Crusade in a Rogue Trader (or Only War or Dark Heresy 2) campaign.

I plan to add rules and even a single phase to those so that one can accomplish more than just military endeavors. I've added things like Holdings (Works like Colonies), Cargo, Trading Fleets, Agents (Businessmen and negotiators), and the Socioeconomic Conflict Phase (which comes right after the Military Conflict Phase) for this. It's the precise details that need to be figured out.

My goal is to convert the rules to something highly characteristic of what a Rogue Trader would go out and do, and not just the military part.