I have been reading this thread with great interest as I live in an area where there is a lot of daylight hours in the summer and only 4-6 hours in the winter. Trying to sleep for 20 hours during the shortest days of the winter months would be impossible here. However, I do find that my energy levels and sleepiness correspond directly with the amount of daylight hours available. During the summer I bounce out of bed at 5 am bright eyed and bushy tailed and now (today) I could barely drag my rear end out of bed at 6:30. Don't know how I'll get through this winter.