You get an extra hour every fall and most of us spend it awake anyway, because our bodies never got the memo. Then for two weeks everything feels off and nobody can say why.

The hour is not really the problem. The light is.

What actually happens to your body

Your internal clock runs mostly on morning light. When the sun starts coming up an hour earlier relative to your alarm, you get a burst of bright light at a time your body reads as night. Then in the evening it gets dark while you still have things to do.

Result: you feel sleepy at nine and wired at eleven, and you blame the time change when really your whole daily rhythm shifted and you did nothing to help it.

What to do in the first week

1. Get outside within thirty minutes of waking. Ten minutes of real outdoor light does more than any indoor lamp. Even on a cloudy day.
2. Keep your wake time fixed. Not your bedtime. Wake time is the anchor, and moving it around is what wrecks people.
3. Dim your lights after dinner. Bright overhead light at nine at night tells your brain it is still afternoon.
4. Get the lamps out now, not in December. Putting a bright lamp on your desk in the morning helps when the sky is gray at eight.

The mistake I made for years was trying to fix it by going to bed earlier. I would lie awake for an hour and then be irritable the next day. Fixing the morning fixed the night on its own after about four days.

Also worth doing this week

• Check your car headlights now that you will be driving home in the dark more.
• Replace smoke detector batteries at the same time so you do not have to remember a second date.
• Swap your summer and winter gear in the closet while you are already thinking about the season.
• Put a lamp on a timer so your living room is lit when you walk in after dark.

None of this is dramatic. But the people I know who sail through the change are the ones who treat it as a light problem and a schedule problem, not a willpower problem.