For a while, and, even now, I tend to have a sleep-cycle where I usually sleep at least twice a day; the weather can and does affect it, whether I eat or not also affects it (sometimes I don't bother eating except for maybe around once every 2-3 days; although this is probably more indicative of not being as physically active as I need to be or should be), when I eat & whether I consume supplements or use deep-sleep herbs is also going to affect energy levels & sleep-quality, then there are binaural-beats & isochronic-tones & out-right brown-noise for sleep-assistance, etc. Anyway...

Sleeping twice a day in segmented blocks of 3-4 hours at a time is apparently... normal...!
That full-eight-hours-in-a-row block-of-hours is apparently only because of «industry» norms...