The verdict

Stop switching. This part is easy.

The twice-yearly change was adopted to save coal in a war and kept to save electricity in an oil crisis. It now saves about a third of a percent of one shrinking category of household energy, and reverses in warm states.

Against that: a measurable spike in heart attacks and fatal crashes every spring, and forty minutes of lost sleep for the working population on the Monday after. The effects are small. They are also entirely unnecessary, which is what makes them indefensible. You do not accept a four to six percent rise in heart attacks and fatal crashes to buy a third of a percent of electricity on the days the policy applies.

About two thirds of Americans have reached this conclusion without reading a single study. They are right.

Then land on standard. Here is the actual reasoning.

We are not going to tell you the health evidence settles this, because it does not. The border studies are observational, they assume schedules stay fixed, and the newest systematic review pushes back on the whole framing. Anyone claiming certainty here is selling something.

What we will say is that three things point the same direction, and none of them depends on a contested effect size.

1. The clock should describe where the sun is. That is what a clock is for. Permanent daylight time is a permanent lie about the position of the sun, maintained for the convenience of evening commerce. If you want later evenings, the honest instrument is to change your schedule, not to redefine what 8am means for 340 million people who did not ask.
2. Every expert body that studies this agrees, and none disagrees. Not a majority. All of them. When the entire relevant scientific establishment lands on one side and the other side's coalition is golf, convenience stores and legislators, that asymmetry is information.
3. We have already run this experiment four times. The United States, Britain, Portugal and Russia all adopted year-round daylight time. All four abandoned it, every time over dark winter mornings. Russia did not even go back to switching. It went to permanent standard time and stayed there. Permanent standard time is the one option nobody has tried and hated, because Hawaii has quietly run it since 1967 and Arizona since 1968, neither with a repeal movement.

And the steelman deserves its due at the end. Evening light really does reduce robbery and pedestrian deaths, and children really do move more. If the country lands on permanent daylight time anyway, it will not be irrational. It will be a decision to buy safer evenings with darker mornings — which is a legitimate trade, and one we should at least make with our eyes open rather than under a name that pretends we are gaining something.

Is this about to be Clock Brexit?

It is the right question, and it is the one that should worry anybody confident here. A lot of intelligent people built this system on purpose. Undoing something you inherited, on the strength of a consensus you did not personally verify, is exactly how a country walks into a mistake it cannot walk back.

Three reasons we think the analogy fails, and one reason it lands somewhere unexpected.

First, the original decision was not deep. It was a wartime coal measure in 1916 and a satirical essay before that, extended in the 1980s and again in 2005 by golf, barbecue and convenience-store lobbying. There is no accumulated wisdom being discarded here. There is a habit.

Second, the cost of being wrong is close to zero. Brexit was expensive and effectively irreversible. A clock policy is a line of legislation and a software update. If permanent standard time proves miserable, we change it back in a session, and we will know within one winter.

Third, we are not short of evidence. We have four national experiments, and every one of them tells us the same thing about which direction the regret runs.

Which is where the analogy actually lands. The Clock Brexit risk is real — it is just pointed the other way.

Permanent daylight time is the option that has been tried and abandoned four times. Permanent standard time is the option two American states have run without complaint since 1968. The bill in front of the Senate is the reckless one, and it passed the House 308 to 117.