Comment by vundercind

My suspicion is a lot of it is due to Winter, and shortening recess times, plus increasing reluctance of schools to send kids outside in anything but perfect weather.

Go to school just as the sun’s coming up -> inside recess because it’s too cold or it’s raining a little -> sunset around 5:00PM.

Schools get kids five days a week for most of the winter, so as parents it’s damn hard to get them outside much while the sun’s up on those days if the schools won’t do it consistently. And you need lots of time in very-bright light to cut your odds of myopia to something very low.