How long people sleep at night depends on the country where they live.

These conclusions were made by South Korean scientists in the course of a study involving 30,000 people from 11 states. Smart devices collected 52 million records of their daily sleep over four years. On average, people go to bed around midnight and wake up at 7:42 am. They sleep the least in Japan - about seven hours, the longest - in Finland. There, the duration of sleep is approximately eight hours.