How long is a turn?

In time I mean, not in actual actions. Thematically speaking, is it a few hours? A quarter-day? A full day? How much is happening to these poor investigators and how fast?

It could be very hectic for their lives if it's just a few hours, on the other hand that will make a trip to the outer worlds a horrific albeit short trip..

it varies - sometimes an hour, sometimes a day, sometimes a week - this is my observation after 6 years of playing (game still going on, think i am doing something wrong).

I agree with DJ. I think the amount of time elapsed per player turn is a variable that changes as it suits the narrative. If an investigator goes from the university to the Curiositie Shoppe and then buys something, that turn might take an hour tops. Someone catching a train over to Dunwich might take several hours. Someone lost in another dimension could be gone for months by his own reckoning, only to return to Arkham and find that mere minutes have passed since he left!

I picture each game like a movie that fades to black and changes scenes after each "important" event (ie: character action.) There's no telling how much time gets "lost" between scenes.