On paper, opening hours are a line on the door and a field on a Google listing. Once guests can order from the table, the same hours quietly become a set of rules about what happens at the edges of the day.

Three different closing times

Most places have more than one, and only ever write down the last of them.

• When the kitchen stops taking food orders.
• When the bar stops serving.
• When the lights go up and the doors lock.

A guest sitting down at half nine cares about the first one. It is the one that stops a table ordering a plate nobody is left to cook.

The night that runs past midnight

A kitchen open until two in the morning is one closing time written across two days, and it is where most hour settings go wrong. If the closing time reads as earlier than the opening time, half the systems in the world decide the day already ended and quietly stop taking orders at eleven.

Whatever you use, set a late night and then check it at the late hour, not at four in the afternoon when everything looks fine.

The day that is different

Almost every place has one: closed Mondays, brunch only on Sunday, the kitchen shuts early on a Tuesday because that is when deliveries land. Those are the days guests get wrong, because the sign on the door describes a normal week.

What else reads the hours

The hours end up doing more work than you set them for. They decide when the table can send an order at all. They mark the boundary of a trading day, so the takings on your home screen add up to a night rather than to a calendar date. They shape the chart that tells you when your room is busiest.

Which means an hour set wrong does not show up as an error. It shows up as a Friday that looks quieter than it felt.

Check them twice a year

Hours drift. Summer opens the garden, winter closes it, the kitchen starts doing Sunday lunch and nobody updates anything. Read them in March and again in September, at the same time as you check what is on the door and what Google is telling people.

The hours on the door are for guests outside. The hours in the system decide what the table can do at half eleven.