Before you start

This is a short book and you can read it in two sittings. It's about one habit, and the habit looks like rest. You get up at half past six all week, and on Saturday you sleep until half past nine, and on Sunday until ten, and by Sunday evening you feel better than you have all week. Then Sunday night you can't get off, and Monday morning the alarm sounds like an accusation, and you spend Monday and most of Tuesday feeling as though you've flown in from somewhere three time zones away. By Wednesday you're right again. By Friday you're tired, and the lie-in seems earned, and round it goes.

I'm going to argue three things. The first is that the habit makes sense from the inside. You are short of sleep by Friday, and sleeping longer is the obvious repair, and the weekend is the only time you can do it. The second is that the lie-in gives you less than it seems to and costs more than it seems to, and there's research on why. A late weekend doesn't only pay back sleep. It moves your body clock later, by something like half an hour to three quarters of an hour over two nights, and on Sunday night your body is being asked to sleep at what it now thinks is half past nine. The Monday feeling is that shift showing itself. Researchers have a name for the gap between your weekday and weekend sleep, and the name is social jet lag, and it isn't a figure of speech. The third is practical. The fix is not less sleep. It's getting up within an hour of your weekday time on both weekend days, getting outside into daylight soon after, and moving the extra sleep you need to the front of the night instead of the end of the morning. Chapters 16 to 19 cover how.

This book doesn't think you're lazy for sleeping in, and it doesn't think mornings are virtuous. Chapter 7 is about the real need the lie-in serves, and chapter 11 is about why a fixed wake time is less grim than it sounds.

Three cautions.

If you do shift work, or you're up in the night with a baby or a small child, or you care for someone who wakes, the rule in this book may not fit your week, and chapter 20 says what does.

If you regularly find it hard to get to sleep or stay asleep, and it's been going on for months and it's affecting how you cope in the day, the NHS says to see a GP, because that's insomnia and it has its own treatment, and a regular wake time is part of that treatment but not the whole of it.

And if you sleep late at weekends because you can't face getting up, and that's been true most days for a fortnight or more, the NHS says to see a GP about your mood, and the weekend can wait until you have.

The notes at the back give my sources and their limits. Where I'm giving my own reasoning and not a finding, I'll say so.