On the other hand, Czech children tended to play video games mainly from 15:00 to 18:00, which is earlier than the first half of subjective night, is around sunset and also includes “dusk” in November at Ceske Budejovice (49°N). Playing video games around sunset may still cause a backward shift in both sleep and wake times, although it is much earlier than the first half of subjective night (around 18:00 ~ 24:00). Honma and Honma (1988) reported that exposure to bright lights from fluorescent lamps from 20:00 to 02:00 caused a delay in the phase of the circadian clock (which controls rhythms such as body temperature rhythms) of adult subjects. In the case of children, exposure to the lights from displays of video game devices even late in the afternoon might relate to the circadian clock phase and plasma melatonin level..