All the reasons you've ever heard for Daylight Saving Time are nonsense. Here is the real one.

by Brian Dunning

Filed under General Science, Urban Legends

Skeptoid Podcast #172

September 22, 2009

Podcast transcript | Subscribe

Listen:

https://skeptoid.com/audio/skeptoid-4172.mp3

Today we're going to turn our clock back (or forward, as the case may be) and screw up our sleep cycles, casting everything into disarray for a good week until we recover — for today's topic is daylight saving time: The myths, the fallacies, and the facts. Why on Earth would we ever want to change our clocks a few times a year? Is it actually a good idea? In today's day and age, is it still good, or is it outdated?

Benjamin Franklin is often credited with inventing the concept of daylight saving time, on the principle of conserving candles. However, a closer look at this popular tale reveals cause for skepticism. Franklin's paper was actually a satire poking fun at the partying lifestyle of Parisians, not a serious recommendation. It was a letter written in 1784 for the Journal de Paris in which he proposed firing cannons at sunrise to wake people up and break them from their nocturnal habits. To justify this, he suggested that sleeping instead of burning candles all night long would save Parisians 64 million pounds of candle wax over six months.

The first serious propositions came independently from different sides of the world a century later: from New Zealander George Hudson in 1895, and Englishman William Wennett in 1907. Both recommendations were to provide for additional sunlit leisure time after work, and it was proposed for use in the summertime only because if it were done in winter, the shorter days would force morning activities (like children walking to school) to happen while it was still dark. That's why we have the current schedule of observing daylight saving only in the summertime: Our workday squeezes into the middle of that narrow band of daylight during the winter, and it drops down to the bottom of the wider band of daylight in the summer; keeping our morning wakeup times roughly aligned with sunrise, but giving us an abundance of extra daylit playtime after work when the days are long enough to permit.

Perhaps the most pervasive popular perception about daylight saving time is that it's all about farmers, the idea being that certain farm tasks should be done at sunrise, whether it's milking cows or watering or harvesting crops, and changing the clock makes this easier somehow. The obvious response to this is that these tasks are going to continue to be done at sunrise, regardless of the time shown on some irrelevant clock. When you dig in and read the arguments for or against daylight saving put forth by various groups, farmers are said to be among the most vocal opponents of daylight saving. Here's a quote that I must have found a hundred times in different sources, word for word:

Farmers, who must wake with the sun no matter what time their clock says, are greatly inconvenienced by having to change their schedule in order to sell their crops to people who observe daylight saving time.

No matter how many times I found that same sentence, I could never discover its original source. The concept is illogical at face value. In the morning hours, daylight saving's effect is to keep the clock more in line with sunrise: i.e., 6:00am comes an hour earlier in the summer when the sun is rising earlier. If farmers need workers to arrive when the sun starts drying the dew, daylight saving is clearly their friend. I found many, many articles repeating the presumption that farmers oppose daylight saving, but almost nowhere did I find a good reason articulated; at least not one that pertains to farming. The president of the New South Wales Farmers Association could only come up with this argument:

Daylight saving has a significant adverse impact on rural families and communities businesses. An example is children traveling home from school in the heat of early afternoon sun. Members also say they have trouble getting their children to bed at normal bed times, and farmers indicate that they work longer days.

...which says nothing about daylight saving creating a problem for the practice of farming. At the same time, other farmers express the same pleasure as other people at an extra hour of sunlit family recreation time after a summer workday.

Dairy farmers have the closest thing to a cogent argument that I could find. Let's say that their product has to be to market at a given clock time, and twice a year the clock changes by an hour. This forces the cows to be milked at a 23 or 25 hour interval, once each year, instead the 24 hour interval to which they're accustomed. Evidently this disruption to the cow's schedule is problematic for the cow. If this really is a significant problem for cows, it constitutes one of only two farm-related arguments against daylight saving that I could dig up.

The other is not unique to farms, and has to do with moving heavy equipment on roads in the early morning. Many such vehicles can only be driven during daylight, and many of the rest shouldn't be operated in darkness for safety reasons. When daylight saving drops the working man's start time down closer to sunrise during the summer, this problem is prolonged for more of the year. But I'm still not convinced by this argument's logic. Farm work starts with the sun. Safe equipment operation starts with the sun. That's how it's always going to be. Daylight saving keeps the clock time at the beginning of the workday more consistent with sunrise year round, so, from a rational perspective, the people who depend on the morning sun for their job have every reason to be the biggest supporters of daylight saving: It brings them better consistency.

So now we come to what everyone believes, and what's written down on paper as the official reason we observe daylight saving time: The conservation of electricity. The idea is that residential power usage is reduced because people don't have to turn their lights on until an hour later in the summer. This was indeed true the first time the question was deeply studied, which was during the oil crisis of the 1970's. The Department of Transportation calculated a 100,000-barrel savings in oil, from a 1% savings in power usage, compared to if we'd stayed on standard time. However, in the decades since then, air conditioning has become much more ubiquitous, and its power consumption greatly outpaces the reduction in lighting — although this is slightly offset by reduced heating on fall and spring mornings. In addition, people have many more electronic gizmos around the house then they did in the 1970's. Having people at home for an extra hour is not nearly such a great way to conserve electricity as it used to be.

Nowadays, people studying power usage during daylight saving get mixed results. There's a lot of regional variation. Places like Florida, with maximum air conditioning needs, clearly use more electricity because of daylight saving; while cooler northern states may still see overall savings due to reduced lighting needs. Generally, reports of national energy consumption combine results from a cross section of utility companies nationwide. Depending on what utilities you include in your report, you may get very different overall results. A truly comprehensive report that accounts for all data is probably outside the realm of practicality.

If you do a Google search for daylight saving energy consumption, you'll find reports are all over the map. In fact, the year after the Department of Transportation found a 1% savings, the National Bureau of Standards reviewed their data and found no savings. Some reports find that it uses as much as 1-2% additional electricity; some find there's a savings of as much as 1-2%. Most fall within the statistical margin of error. The one statement I'd feel comfortable making with authority is that any possible energy savings that may be derived from daylight saving time is statistically insignificant.

There's one powerful reason that daylight saving is probably here to stay, and it has nothing to do with farms or electricity or road safety. Strong reasons usually have to do with money. Not money that you send to your utility company, but money that you hand over at the cash register. During the warm summer months when it's possible to do so in comfort, people like to be out and about in the evening. They like to go out for dinner, drinks, or a movie, or wander through stores and galleries. They also like to play golf and tennis. Whenever they do these things, they spend money. Lots of money, in the collective. Give them an extra hour to recreate in the summer, and they spend even more money. In 1986, an extra month of daylight saving was added to the calendar, and representatives of various recreational industries appeared in front of Congress to testify about the effect it had on their bottom lines. The golf industry is said to have benefited by an additional $200 million, just from that one additional month; and the barbecue industry is said to have sold an additional $100 million in barbecues and charcoal briquettes. The additional extension in 2007 into November was supported strongly by the candy industry, who can sell a lot more Halloween candy when kids can spend an extra hour trick or treating before bedtime.

There is even a certain lobby out there that points to the environmental impact of this extra hour of shopping, dining, and golf. One paper from UC Santa Barbara calculated the cost of the resulting pollution as several million dollars per year. Whatever your particular fancy, you can probably find someone who's written a paper saying that daylight saving is good or bad for it. Daylight saving is one case where the fewer words you use to describe it, the more accurate you are. One word: Money. The more details you go into beyond that, the more treacherous your footing.



By Brian Dunning

Follow @BrianDunning