Artificial light has transformed how the human race has lived in the past 100 years or so. It’s estimated that between 1950 and 2000, exposure to artificial light in the UK rose four-fold. Even for those not working night shifts, it can be almost impossible to avoid the night-time glare from street lamps, car lights, TVs, computers and smartphones.
http://www.dailymail.co.uk/health/article-2800593/how-light-night-make-ill-scientists-learn-effects-of.html