Yes, less sunlight means more sleep!
At Fullpower Labs, we looked at the data. The Fullpower dataset includes 250 million nights of sleep. Sleep information from the Sleeeptracker Monitor is unique because it is fully contactless and non-invasive, yet still accurate to within 90%+ gold standard polysomnography. Data shows that continuous heart rate averaged throughout the night is minimized with 7.5 hours of sleep. From there, we find that on average, the answer to our question is 10.8% of deep sleep and 25.3% of REM sleep.