How long for one turn? Is it one day, one week, one month or one year?

In the first game it was supposed to be a year, though I'm not sure if that's the case anymore.  I mean it might be, considering that that's the only way the population growth makes sense.

I think a galatic turn is based on a players own preferences, and since most turn based games are roughly a year per turn (sometimes a month to 4 months), its somewhere aroumd there. Time could also fluctuate differently based on how fast you complete the main faction quests or the academy quest. Also, the planets orbiting cycles are probably not the same as Earths so a year for one faction could be longer or shorter than a year here. 

In summary it’s whatever you want it to be 

Suis3i wrote:

... 

In summary it’s whatever you want it to be 

This is pretty much it. It was originally a year, but that seemed a bit too long. So it is generally somewhere in the 3-4-6 month range, I think, if we imagine how long the various things would take to construct... but it really is one of those things that's flexible in the universe.

-Slow

The amount of dust pollution present in everyone's nervous system (hence the Essence mechanics) makes lifespan long enough to make the relativistic effects of mass FTL travel tolerable.

If 3-4-6 month range kinda make sense. An era where being have an understanding for Baryonic principles, transfer consciousness to dust and even terraform a planet. For a year per turn kinda slow actually.