In his book, Roenneberg points out a whole range of different aspects of sleep, ranging from day-to-day life to the evolution of sleep. But the book doesn’t merely focus on sleep in itself, it encompasses the biological clock and the time of day when we sleep best and when we can’t and shouldn’t sleep. Roenneberg argues that increasing the awareness of the importance of sleep is not only up to the individual but also a social and political responsibility.
From “night owls” to “early birds”, everyone has a right to sleep according to their body clock. Roenneberg shows that "alarm clocks" are actually "harm clocks", in that they are responsible for decreasing our health. If we cannot ban them, we should at least try and decrease their usage in changing the flexibility of work times.
If we wake up when our body is ready, we have more energy throughout the day, are more productive, healthier and potentially live longer.
For decades Roenneberg conducted research on body clocks and their importance for sleep and wellbeing. With the help of questionnaires, he created a database about sleep behaviour with about 300.000 entries from all over the world. He showed that late teenagers are not lazy but follow a biological programme and discovered the modern syndrome of “social jetlag”.