Most people can name the week it started

Within the first hour, most people can tell me the week it started.

They do not expect to. In the first five minutes the answer is usually a shrug: a couple of years, since the spring, it just crept up. Then I ask what else was going on around then, and the shrug goes.

The answer comes out like this. A Thursday in late October. Drizzle, the wipers on the slow setting, the engine running in a depot car park. The song on the radio was halfway through, and they can still tell me which one.

Most are surprised by their own precision. Some apologise for it. Some laugh, then stop laughing.

Many tell me the song has not been played in their car since, and they change station before the chorus. The rest is small things: the colour of the car in front, what was in the footwell, whether the window was down. People forget birthdays and remember that the heater had just come on.

If you drive a van round Kent, sleep badly and tell everyone you are just tired, you may already have a date like this. You have probably had it for years. It is clear, it is detailed, and you have not said it to anyone.

People are surprised by how much they know about that one week, and how little about the weeks on either side of it.

The week itself is sharp, down to which way the car was facing. I notice it in nearly every first hour, and I have stopped being surprised by it. Some lead with the weather. Others lead with the song, or a smell: coffee gone cold, wet coats on a radiator, the inside of a hot cab.

People tell me they have gone over it hundreds of times, usually alone, in the car or in bed. Said aloud as a date, it sounds smaller than it has felt, and a fair number go quiet for a moment.

What I do with the date

I write it down. Month and year at least, the day if you have it, on a line of its own at the top of the page, with the weather and the song beside it.

Then I ask what else was going on around it. Where you were living, who was in the house, what the job was like that autumn, what had just ended and what was about to start. People answer slowly at first.

Within the hour the page has filled in around that one line. Sometimes the date turns out to sit a few weeks away from where the person has always placed it, and I write both down.

I do not hurry this part. The date has usually only ever been said inside someone's head, so what comes out is the first time it has been put in order.

That line is where the work begins. I come back to it in later sessions, and it stays at the top of the page.

Some people ask to see what I have written. It is a single line with a month and a year on it, and they read it for longer than a line needs.