Over a lifetime, you find yourself doing many different things at 9pm: watching TV; reading a book; sitting in a pub; leaving a restaurant to go to a cinema, or the other way round. When you have young children, nine o’clock generally marks the start of the precious time you call your own – a tiny window into which you must cram all your fun. As I’ve aged, I’ve come to associate the 21st hour of the day with coming home rather than going out. But there is one thing I’ve never contemplated doing at 9pm: going to bed. And yet, according to the Wall Street Journal, 9pm is the hot new bedtime – not for middle-aged tired people, but for twentysomethings. The young people of today, it seems, are taking control over their sleep routines and prioritising shuteye over fun. A 2022 analysis found that Americans in their 20s were getting, on average, nine hours and 28 minutes of sleep a night, up from eight hours and 47 minutes in 2010. The WSJ quoted …