This is one of the reasons the system has us schooling and working in buildings with no access to the sun during those vital sun hours of the day. I personally went from working a sales delivery job for 12 years where I was outside for vast majority of my 12 hour workday and was always full of energy. My next jobs had been inside buildings from 6am to 6pm with no sun and I was forever exhausted even on my days off. It's interesting thinking back on it now the mental decline after changing jobs was incredible partly because the job was a bad fit, but I believe mostly because I never had any sunshine and I thrived on that.