If we are talking about humans and the hormones associated with the 24-hour sleep/wake cycle, they are largely influenced by blue light which is in the visible

If we are talking about humans and the hormones associated with the 24-hour sleep/wake cycle, they are largely influenced by blue light which is in the visible spectrum. It's part of why screens without orange-shifting software will tend to keep you wide awake at night. Interestingly, red wave (IR) light appears to influence cortisol levels but not melatonin. [1] IR also makes it through windows as any cat can attest. Getting outside for an hour or two as often as possible, regardless of the season, is probably a good idea, but it doesn't appear to be strictly necessary for modulating circadian rhythms. [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2905913/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2905913/