High noon for summer time


The United States Senate has passed the “Sunshine Protection Act,” a bill to make daylight saving time the standard time and do away with annual time changes. While I can support the second half of this motion, in my opinion redefining daylight saving time as standard time is nonsense.

It’s particularly funny timing, right around the vernal equinox, when the sun is at its highest at noon standard time, to debate calling this time “one PM” forever.

Right idea, wrong time

Let’s give a quick overview of the good idea here – getting rid of time changes. These are known to cause sleep disturbances, leading not only to sleepy heads on Monday mornings, but also to an increased risk of heart attack and accidents in general. When researchers look at the data, it’s the “jumping ahead” that causes problems. People who have slept an hour longer don’t seem to suffer as much as people who have lost one. Go figure.

So maybe it makes sense to stop changing times. If we settle for one standard time, do we choose Standard Time or Daylight Saving Time? Admittedly, this is a totally unfair way of asking the question, but there are some good reasons to prefer year-round standard time. The biggest is winter. In short, it’s hard enough getting up on a cold January morning when the sun doesn’t rise for another hour or two. Add to that an hour of darkness and you know why the two previous attempts to run Daylight Savings Time all year round were short-lived. And why the Swedes drink so much coffee.

“France-002886 – Sundial” by archer10 (Dennis) CC BY-SA 2.0.

There is also the fundamental logic behind our measurement of time that has persisted for centuries and is embedded in most of our cultural references to time. Ante Meridian and Post Meridian. High Noon, when the hour hand on the clock points straight up, represents the sun itself. But even before the clocks, the sun’s halfway point on its daily journey marked the day’s halfway point. That is not only why we have lunch when we do, it is the origin of the telling of time by man himself.

If we permanently change the definition of noon, we have disconnected time from the sun. How are we going to explain time to future children? I accept daylight saving time when we start reprinting analog watches with 1 o’clock at the top and start referring to 12 o’clock as the one just before the sun reaches its peak. As soon as “one afternoon” replaces “twelve afternoon”, I board. At midnight, when the clock strikes one, I don’t get the same shiver down my spine. Sorry, Dracula.

If culture and physics point to standard time, why would you want daylight saving time to become the new norm? When people think of summer time, they naturally think of those beautiful long summer days that extend into the night. My personal guess is that many people confuse daylight saving time with daylight saving time. Heck, even the bill’s name suggests protecting the sun itself, rather than just spinning it clockwise. These are not good reasons.

The economy

The good reason behind the DST proposal – indeed, the original reason – is to save energy. And this probably made intuitive sense in the 1950s, when a significant amount of energy was spent on lighting. But these days, when non-sleeping people turn on the air conditioning, even if their lights are still off, it’s not so obvious. For a long time there were no empirical economic studies on daylight saving time, until 2008, when there were, and then the situation did not remain completely clear.

In 2007, the Energy Policy Act of 2005 went into effect, extending U.S. Daylight Savings Time by a few weeks on the one hand and a few days on the other. And while it was a minor inconvenience for normal people to remember the new data, this kind of change in a system is an economist’s dream. In a field where land-scale experiments are banned, these kinds of external changes offer the best chance of finding out how things work. Something has changed in the system, what are the results?

The United States Department of Energy (DOE) released a report to Congress (PDF) in 2008 that analyzed the national impact of the change. They note a saving at night that is slightly greater than an increase in energy demand in the mornings, in the summer. They also note that more savings are made in March than in November. Their conclusion was that there was a daily energy saving of 0.5% due to daylight saving time. Overall, the new policy has saved the US 0.03% of annual energy demand. Not really overwhelming, but not nothing either.

Another empirical economic study on daylight saving time came out in 2008. This article was based on household-level evidence from Indiana, which had the peculiarity of introducing daylight saving time both before and after the 2007 national change by county. Some counties switched to DST, some switched to DST and some didn’t switch at all. This allowed the researchers to make a much more direct comparison of “treatment” and “control” groups in different provinces; they chose Indiana because it was the perfect natural experiment. Their fine-grained dataset also allowed them to break down total energy consumption into a few categories. They found a 1% daily increase in energy expenditure. As you would expect, electricity for lighting fell, but was more than compensated for by heating and cooling.

Both studies agree that daylight saving time actually increases energy use from sometime in early fall. And while none of these studies focused on answering the right question: What would happen if we extended daylight saving time into winter? — they both suggest it would be the opposite of saving. Making daylight saving time permanent will not save you any energy. And depending on which of the two studies you believe, it can get rid of it altogether.

What must we do?

So if you asked Aristotle, he would side with me. In the afternoon the sun is at its highest and the planets revolve in perfect circles. (Okay, scrap that.) If medicine points to using only one time standard, then astronomy as well as linguistics, watchmaking and cultural traditions all point to Standard Time as the right choice. The economic effects are somehow unlikely to be that significant, and will likely depend on future relative efficiency gains in lighting versus air conditioning. (Happy predicting that.) All I know is that daylight saving time is confusing my sundial right now.

But how am I going to sell Daylight Saving Time back to people who think they literally “save daylight” or “protect sun”? To people who have heard that daylight saving time saves energy all their lives, whether it is demonstrably true or not? To people who confuse longer days in the summer with lies about the funny numbers on a clock? Silly message.

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