I have been a night owl from childhood until I turned 46. My natural sleep time is 12:30 - 1 am and my natural wake up time is 9 - 9:30 am. After having kids and waking up early to drive them to school, my work suffered and I spent the entire day in a daze, but oddly I would get a 2nd wind around 11 pm. I always knew that animals go to sleep and wake up in a rhythm, called the circadian rhythm. Exposure to sunlight controls this rhythm. After 35+ years of being a night-owl, I am now a hummingbird (lark=early riser, hummingbird=normal riser, owl=late riser). I also want to mention that as a typical owl, I can sleep 8 hours just fine at 1 am and wake up feeling refreshed at 9-9:30 am. Practicing good sleep hygiene to try to go to bed before my "natural" bedtime never worked and actually made me frustrated.

I finally shifted my rhythm to 11 pm - 7 am by reading "Reset Your Inner Clock" by Dr. Michael Terman. He and his team have been researching circadian rhythms for several decades. He has a website where he has a self assesment to measure how owl-ish you are: - Center for Environmental Therapeutics

Dr. Terman's book goes into case studies of extreme owls, going to bed at 7 am and waking at 3 pm. That's extreme! I'd like to point out that some people have poor sleep due to restless legs, sleep apnea, and other causes. Resetting your rhythm only works if you naturally have good sleep, but just shifted out of alignment with your job. If your job is being a jazz musician or bartender, then you will have a big problem if you are an early bird. The book also goes into resetting your clock so you go to sleep and wake up later, which is a common problem for older people or a lark-ish actor that must have peak mental alertness during their evening performances, but most people are owls needing to reset earlier.

If you naturally go to sleep from 11 pm - 7 am, then you are a normal hummingbird. 70% of people are hummingbirds. Getting up at 5 am means you want to be a lark. If you gradually shift 15 minutes per day, it will take 8 days to shift 2 hours earlier, which is definitely possible and commonly done.

Eating times, social activities, and alarm clocks are a very weak signal to control circadian rhythms but the main signal is sunlight (or artificial sunlight). Many blind people have non 24 rhythm disorder, where they go to sleep an hour or so later every day. After 24 days they have gone from sleeping at night to sleeping in the day and then back again. They effectively chased the clock around. This is because the internal rhythm is not exactly 24 hours and the weak signal is just not enough. Non 24 rhythm disorder is treated with melatonin, but melatonin is far weaker in resetting rhythm compared with sunlight or artificial sunlight, but still stronger than social activities or eating timing.