LOL!!! Man this brings back memories, me and my drift team did this once, we even cheated and put our screens and max brightness and it was still pitch black, we eventually started playing red triangle vs blue triangle on the mini map or paused the let the cars drive on their own until we could see again.
When we could see it took about 11-12 minutes to do one lap but once it got dark it took about 20 minutes (pitch black). Took us about 45 minutes to do 3 laps with a full day night cycle. We didnt finished because i think we ran out of gas.