Most amateur astronomers have a love-hate relationship with the annual switch to and from "summer" time. One thing's for sure: Everyone has an opinion about it!
Some years ago, a local community organizer asked me to help her find some dates and times for family-friendly star parties over the summer. One problem, I said, is that here in Massachusetts the midsummer Sun doesn't set until after 8 p.m. and it doesn't get fully dark for at least another hour. It's challenging for young children to stay awake so late into the evening. "You can blame daylight-saving time," I told her.
I don't know about you, but our annual switch to daylight time (called "summer time" most everywhere outside the U.S.) does amateur astronomy no favors. Most nights, by the time Sagittarius is up high enough to be seen well, I'm ready to put my head down for sleep.
Things were bad enough — "springing ahead" in April and "falling back" in October — but a few years ago Congress meddled further with Mother Nature when it passed the Energy Policy Act of 2005 and decreed that daylight-saving time would be extended, beginning in 2007. Now the U.S. observes summer time from the second Sunday of March until the first Sunday in November, which is about two-thirds of the year. Canada followed our lead, but European countries typically wait another three weeks to make the switch and Mexico another four.
In fact, although 70 countries (or parts of them) observe some form of summer time, it's mostly a high-latitude phenomenon. Most of the world's population avoids it altogether, and of course when northern countries are using it, our friends Down Under are not.
So how did all this come about in the first place? During his time as America's envoy to France, Benjamin Franklin once famously (but anonymously) wrote that Parisians could economize on candles by firing cannons at sunrise to get the populace on their feet sooner during summer.
But the tongue-in-cheek Franklin didn't propose changing clocks. For that, I blame golf.
Let's turn back the clock to 1907, when Englishman William Willett published The Waste of Daylight. It seems that Willett, an avid golfer, wanted to spend more time after work perfecting his putting. So he proposed advancing the clock by 20 minutes in spring and fall and by 80 minutes in midsummer. His idea didn't take hold until World War I, when many nations briefly adopted daylight time to conserve energy. After that DST was off-again, on-again here in the U.S., making a comeback during World War II, until Congress made it permanent in 1966.
Remarkably, this time-honored practice has been, and continues to be, controversial. Arizona and Hawaii keep standard time year round; until recently most of Indiana did too. Farmers don't like it. Backyard astronomers don't like it. The date switch in 2007 cost an estimated $500 million to $1 billion. Twice-a-year clock shifts cause confusion, disrupt your sleep, and, according to multiple studies, even increase your risk of a stroke or heart attack.
DST Means Energy Savings — Not!
The usual justification for advancing the clock is energy savings. The logic here is that by having more daylight in the evening hours, we use less lighting. But in 1966, when DST became the law of the land, air conditioning wasn't nearly as pervasive as it is now.
At the request of Congress, the Department of Energy analyzed the effects of daylight time's extension in 2007 and concluded that there might be an energy saving of 0.5%. But other findings challenge that assessment. Some studies show that daylight time causes us to use more energy, because we run the AC longer in late afternoon during summer and need more heat on sunless spring and fall mornings.
In 2008, researchers Matthew Kotchen and Laura Grant (University of California, Santa Barbara) detailed what happened when Indiana caved in and adopted daylight-saving time in 2006. They find that Indianans' energy bills rose about 1% overall after the switch — and 2% to 4% in late summer and early fall. As Kotchen later concluded in a 2014 op-ed for the New York Times, "a growing body of evidence reveals that daylight saving time increases rather than decreases energy consumption."
And more than a few countries — including Argentina, Iceland, Malaysia, Turkey, and even most of Canada's Saskatchewan (arguably as large as many countries) have switched to summer time year-round. Hey, who am I to argue with already flash-frozen Saskatchewanians who don't get to see sunrise in December until after 9 a.m.? Russia went to permanent DST in 2011 but then cried "Nyet!" and switched to permanent standard time three years later.
Closer to home, several states are toying with permanent summer time (in fact, last year Florida's legislature made it official by passing the "Sunshine Protection Act"). But while states can follow the lead of Hawai'i and Arizona, embracing standard time 24/7/52, it'd take an act of Congress to allow them to observe daylight-saving time year-round.
So the debate goes on. If Congress listened to me instead of those clock-watchers at the Department of Energy, we'd do away with this time-warp nonsense.
This post originally appeared in 2009 and has been updated with recent policy events and scientific research. See the excellent article in Wikipedia for more information on Daylight Saving Time.