Well, it depends... I've used two different time lapse intervals in these videos. The ones where the clouds were moving rather quickly are taken at a single frame every 10 seconds. The slower ones are at a single frame per second. The standard frame rate of my camcorder is 29.97 frames per second, I believe. I tried to figure this out a while back in relation to a driving video I did using time lapse to guess at the equivalent perspective of the speed of the car, but my figures just didn't come out right. So maybe someone else can figure out the real amount of time involved.
For the 10 second intervals I would try to set up the camcorder around maybe 9 or 10 am and let it run till just past sunset, which was around 8:15 pm or so. With the 1 second interval videos, I would normally set that up when the sun was already fairly close to the horizon, so maybe around 5 or 6 pm. Bear in mind that I was on the beach without a watch on, and time was rather irrelevant for the most part to me.
So I'm just guessing at the times here.
I would like to set up some time lapse video from before sunrise till after sunset, but the camcorder has a limit on continuous runtime of only 12 hours. So I would have to do this in the Winter months, I suppose. Of course, I have to be on the AC adaptor, as the battery is only good for just over 3 hours.