Built on Facts

Savings Time?

Imagine the scientists of the world got together and decided they didn’t like the meter as a unit of distance. They were tired of traveling such long distances to conferences and decided that by redefining the new meters as two old meters, suddenly the plane flight was only 1000 kilometers instead of 2000 kilometers.

I don’t think it’s very plausible. Nonetheless, we do pretty much the same thing when we change back and forth between daylight savings time and standard time.

Now there are some good arguments for the change. It means kids don’t have to stand in the dark waiting for their school bus in the winter. It means parents have more daylight to share with their family after work in the summer. There’s other advantages in that vein.

But it seems to me that you could get those advantages without actually changing the clock. Why not just have school start and end an hour later? Why not let businesses that don’t involve daylight decide to shift or not shift depending on the preferences of their work force? It might be unworkably confusing, and it could be that in the absence of an official time change most private enterprise would stick to a constant schedule anyway. I really couldn’t say. There is a possible advantage to individual businesses having different schedules – travel. If half of businesses decide they’re going to keep operating from 9-5 and the other half operate from 8-4, then it could be that rush hour would become not-so-rushed two hours. It could reduce congestion. Maybe. I’m hardly a traffic engineer though, it’s a just a hypothesis.

We physicists tend to be connoisseurs of units, and a constantly changing time standard grates a bit. To be perfectly honest that’s my main slightly quixotic objection to the time change. Opinions?


  1. #1 Eamon
    March 9, 2009

    The staggered opening hours was kicked about in the UK maybe a decade-or-so ago. Businesses just weren’t keen on having to keep synch with whoever was in late-mode (or conversely, early-mode).

    Basically a good idea though. If only scientists ruled the world…

  2. #2 Larry Ayers
    March 9, 2009

    I think the twice-yearly time change is archaic, a remnant of the largely-agricultural population of the past, and it should be ditched. It’s just a pain in the butt.

  3. #3 Rhett
    March 9, 2009

    Daylight savings doesn’t effect kids standing at the bus stop during the winter because that is normal time (or what is called – standard time?) Daylight savings is now, not then.

  4. #4 D. C. Sessions
    March 9, 2009

    I think having more time in the summer after work when you have to stay inside waiting for it to cool off would be damned stupid, and cutting short the only decent time of day (around dawn) to go to work an hour earlier is just insane. Then again, I happen to live in a place where we don’t screw around with the clocks.

  5. #5 Eric Lund
    March 9, 2009

    There is a possible advantage to individual businesses having different schedules – travel. If half of businesses decide they’re going to keep operating from 9-5 and the other half operate from 8-4, then it could be that rush hour would become not-so-rushed two hours.

    IINM this is already being done in some large cities in the US. Companies that can allow their workers flexible schedules allow some of their workers to work 7-3, others 10-6, and various possibilities in between. For businesses with shift schedules, the shift start times vary: some start the day shift at 7, others at 8 or 9 (and this is in New Hampshire, where traffic congestion is usually less severe than many other places).

    I agree that it is a big pain in the neck. First, you get the agony of jet lag without actually going anywhere. Second, and more important, is that the effective dates of DST (where it is observed at all) vary by location.

    The states of Arizona and Hawaii do not observe DST (this used to be true of most of Indiana, but I think they now observe DST). Neither do most Asian countries, including Japan and China, which are at high enough latitude to benefit. Europe’s transition dates have been different in the past (I don’t know if that is still true). Southern hemisphere countries that observe DST obviously do so during austral summer; thus, for example, the time difference between New York and São Paulo can be 1, 2, or 3 hours depending on the time of year.

    The one argument in favor of DST is that it reduces demand for artificial lighting–this was the argument Ben Franklin made when he first advocated DST. Most people are more likely to be awake at 8 PM than at 5 AM, so you can reduce electricity demand by letting these people use natural light later in the evening, and spend less of the morning with the curtains drawn while the sun is shining. But this is an argument for keeping DST in effect year round, not for switching back and forth.

    As for the problem of kids waiting for the bus in the dark: Even under standard time, kids in northern states have to wait for the bus in the dark in December and early January. Sunrise times around the winter solstice are about 7:10 in New Hampshire (it’s this early because we are well east of center in our time zone) and 7:45 in the Seattle area.

  6. #6 Uncle Al
    March 9, 2009

    How do you know traffic is being controlled unless it is being controlled badly? Shifting the time background on command has subtle imposed social undertones useful to rulers. Clocks in our house: two cars, two alarm clocks, five wristwatches, a wall clock, stove and microwave, light timers; TV and its pile of feed-throughs. Check the computers.

    Plug in the Oregon Scientific clock that synchs to Colorado, get it locked, one wristwatch is the secondary standard that sets the house. Chipping every timepiece with a sych button or command (eats batteries if continuous) would make sense – so it is never built into electronics. Stooopid.

  7. #7 MRW
    March 9, 2009

    “I think the twice-yearly time change is archaic, a remnant of the largely-agricultural population of the past, and it should be ditched. It’s just a pain in the butt.”

    Except that it has nothing to do with agriculture. Farmers tend to be *anti*-daylight saving time.

  8. #8 Chris
    March 9, 2009

    There’s a related proposal that really whacks your head if you’re used to consistent standards. Get rid of the Mountain Time zone. You would have a two hour jump between Central Time and Pacific Time somewhere in the middle of the intermountain west.

    It sounds insane, but when you take a second look it’s not. MT is relatively unpopulated and ranchers are going to be tied to the solar time anyway. There are only a few urban areas and they could easily go with adjacent TZ. (E.g,, Idaho and Utah go to PT, Wyoming, Colorado and New Mexico go to CT, and Montana is split.) It often feels like the rest of the country forgets we’re here anyway.

    A few years ago there was discussion of metro Denver (not the entire state) going to CT, and one of the biggest concerns ironically showed the problem with inconsistent schedules. Major airports operate on a national schedule, especially at hubs since you want to schedule flights to maximize connections. E.g., you want flights from NY and LA to arrive in Denver at about the same time so passengers can make connections to the other city. That’s not a major concern any longer since the airport has been moved to a rural area.

    Sounds good, but at the time the Denver airport was surrounded by housing and the airline schedule would not be (easily) affected by the change to CT. The net effect would be that a lot of ‘early evening’ flights would become ‘late night’ flights.

  9. #9 Eric Lund
    March 9, 2009

    There’s a related proposal that really whacks your head if you’re used to consistent standards. Get rid of the Mountain Time zone. You would have a two hour jump between Central Time and Pacific Time somewhere in the middle of the intermountain west.

    This actually sounds less crazy than some time zone contortions that already exist.

    Australia: Has three time zones, but their central time zone is only 1/2 hour behind their eastern time zone. Thus you have a 1.5 hour time jump as you enter/leave Western Australia.

    China: The entire country runs on Beijing time. By longitude, Harbin should be one hour ahead, Xi’an one hour behind, Urumqi two hours behind, and the far west three hours behind. This gives you a time jump of three hours crossing the border with Pakistan and 2.5 hours crossing the border with India.

    Europe: Most EU countries are one hour ahead of the UK, including three countries (France, Spain, and Portugal) which are partially or entirely west of London’s longitude.

    Newfoundland: There isn’t any particular obvious reason why this Canadian province isn’t in the same time zone as Nova Scotia, but it is 1/2 hour ahead.

  10. #10 rob
    March 9, 2009

    daylight savings time? you don’t save any daylight.

    it’s like trying to be taller by cutting your head off and standing on it.

  11. #11 Dan J
    March 9, 2009

    I had to buy a new alarm clock to replace one that automatically adjusted for DST because the dates for transition were hard-coded in the firmware, and then they changed the dates. They may change the dates back again based on research into whether or not it saves more energy. As far as I know, there’s still no evidence showing that DST actually saves energy.

    Getting rid of DST is (IMO) a very good idea. One other thing that I think is a good idea is to move the boundaries of the time zones closer to where they are supposed to be. The division between Eastern and Central in the US is particularly messed up.

    If the proper changes are made, the new midnight doesn’t have to start “on the hour” of the old clock, meaning that we could split the difference with the extra daylight availability. Just like adding an extra second to match the clocks with the earth’s rotation, we could add an extra 30 minutes before midnight on 31 December so that the new year would start out a little saner, and we’d never have to adjust our clocks back and forth like this again.

  12. #12 CRM-114
    March 9, 2009

    Although I live in California, I do not observe Daylight Saving Time. Instead, I switch from Pacific Standard Time to Mountain Standard time, and I do everything an hour early. So far nobody’s caught on.

  13. #13 Michael F. Martin
    March 9, 2009

    DST is of dubious merit. People wonder why dairy farmers complain, but living creatures run in circadian rhythms that are interrupted by a phase shift like DST.


  14. #14 Rick Pikul
    March 9, 2009

    Newfoundland Time has historical reasons: When time zones were created Newfoundland was not part of Canada, (and would not be for over half a century). Thus there was no reason to sync with Nova Scotia.

    The half-hour difference comes from the fact that the government, most of the population, and virtually everything that actually cares about what the clock says has always been out on the extreme east end of Newfoundland, where the solar time is smack-dab on the ‘proper’ division between -3 and -4.

    Personally, I would rather see Sir Sandford Fleming’s original proposal be used: One time for the entire planet, no time zone conversions needed.

  15. #15 Chris
    March 9, 2009

    The animals are messed up by the farmer/rancher changing his schedule, not the time change itself. There’s nothing that says the cows have to be milked at 7 AM.

    (Well, yeah, if it’s a family farm and the children have to do their chores before heading off to classes starting an hour earlier… but you get the idea.)

    On the bigger picture, I’ve gone from a technocentric to legal perspective as I’ve gotten older. E.g., defining CIVIL spring as the months of March, April and May instead of referring to the solar equinoxes and solstices. What do we gain by using the latter definitions, really? It definitely doesn’t help climatologically since the weather is about “one month ahead” of the solar season, e.g., you do not think ‘autumn’ in mid-December, or think ‘winter’ as you see plants turning green again.

    Same thing with solar time vs. DST. All that really matters is that our times are somewhat synchronized with each other, and if it makes the most sense to use DST then that’s what we should use without regard to our actual longitude.

    BTW there is already some time-shifting in the middle of the country. Prime-time in CT is usually 7-10 since it’s the same actual time as 8-11 ET — one broadcast will cover over half of the country. Agriculture is also a factor since people who have to get up early will also tend to go to bed late, so they’ll want an earlier prime time. This can become a circular argument though since many urban people will find it easier to get up early. I know a lot of other people who get up before 5, but this usually shocks people on the coasts. Then again I’m usually asleep before 10.

  16. #16 dWj
    March 9, 2009

    Milton Friedman drew a comparison between DST and floating exchange rates; if a country is running an unsustainable trade deficit, it might need to lower all of the prices of its domestic goods relative to prices outside the country, and changing just the size of the unit (by devaluing it) creates a much smoother transition than the dislocations involved with an uncoordinated period of deflation. Similarly — and this is where I agree with you, farmers, and most of the commenters — supposing that we thought it would be a good idea for businesses to switch to earlier hours in the summer than in the winter, changing the clocks is probably a much smoother way to handle it than have each business change its stated hours in either a coordinated or uncoordinated way.

  17. #17 theGomezSymbol
    March 9, 2009

    Daylight Savings is not a change of units themselves, but a change in your reference system.

  18. #18 Michael F. Martin
    March 9, 2009

    “All that really matters is that our times are somewhat synchronized with each other, and if it makes the most sense to use DST then that’s what we should use without regard to our actual longitude.”

    The problem with this argument is that living things do not have clocks whose phase may be adjusted at will.

  19. #19 catgirl
    March 9, 2009

    For me, Daylight Saving Time is trading my morning sunlight for evening sunlight. For the past few weeks, it has been somewhat light when I woke up in the morning. This morning, it was completely dark, and that makes it very difficult for me to wake up. Soon enough, it will go back to being light when I wake up, but until then I will hate mornings even more than usual.

  20. #20 Roger Sweeny
    March 9, 2009


    I’m with you. DST makes sense in a few weeks when there is enough sunlight in the morning to shift an hour of it to the evening WITHOUT MAKING ME GET UP IN THE DARK.

    The first Sunday in April seems about right.

  21. #21 Peter
    March 9, 2009

    I am just amazed that about half a billion individual humans can be persuaded to do anything in sync. With the odd exception we all made the switch this weekend whatever the time zone we were in.

  22. #22 MPL
    March 9, 2009

    There’s actually a whole book on the history of daylight saving time: “Spring Forward: The annual madness of daylight saving time” by Michael Downing. Basically: farmers hate it, retailers and sports franchises like it, and everyone’s confused by it. The history of time zones is surprisingly convoluted too (Chicago wanted to be on New York time at one point).

    Supporters of DST have always claimed huge energy savings and safety improvements, but seeing as it just amounts to getting up an hour earlier, you’d think that if it were so great, everyone would already be working on an eight-to-four schedule in the summer.

  23. #23 Michael F. Martin
    March 9, 2009

    Perhaps I could have been more precise. Per Peter’s remark it’s both amazing and true that we do adjust our phases in sync. My point is that it’s not comfortable!

  24. #24 Wayne
    March 9, 2009

    You could always adopt French Revolutionary decimal time: http://en.wikipedia.org/wiki/Decimal_time#France. ;-)

  25. #25 Paul Murray
    March 9, 2009

    Daylight Savings time is a great way to get the whole of a society to take advantage of those extra hours of daylight at the start of the day during summer. It gets everyone – absolutely everyone – to reschedule their daily acivities in synchrony. That is, unlike your airplane example, it has a real effect – although one that’s about human activity.

    The peeople who don’t like it are
    a) farmers, and other people who work with nonhuman diurnal things.
    b) people who live in states nearer the equator
    c) people who just find it to be a huge annoyance.

    Point a) is worth particular notice. DST is not an agricultural hangover – quite the reverse. It’s an urban thing, and country people tend to dislike it. They get up at dawn, anyway – so have natural daylight savings: their daily shchedule shifs with the seasons. In fact, that would be a great alternative to DST: just fix the time “6AM” to sunup, in whatever latitude. Mind you: it might cause problems for the norgegians.

  26. #26 MPL
    March 9, 2009

    Re: No. 25

    Actually, adjusting the time to fit between dawn and sunset was the most common system historically. Usually, each hour was 1/12th of the daylight. Most cultures that used adjustable hours were located closer to the equator, where they varied less than they would up north.

  27. #27 samantha
    March 9, 2009

    I hate DST! I get a touch of depression in winter, and I’m fine with waking up in the dark (actually, I kind of like it – makes me feel productive!), but I can’t stand coming home from work and there being no light. terribly depressing.

  28. #28 Azkyroth
    March 10, 2009

    I have an 09:00 class that just became an 08:00 class when the clocks change. My body’s circadian rhythms seem to be fairly inflexible and getting myself out of bed in time for the 09:00 class required an almost violent effort. As far as I’m concerned right now, enforced observation of daylight savings time, like the manufacture of musical children’s toys with no “off” switch, should be considered Crimes Against Humanity.

  29. #29 Kobra
    March 10, 2009

    This is a bit OT, but I can’t think of anyone who would appreciate this joke more than the readers of this blog.


    Although, arguably, they should have gone one step forward (add “the fourth one ask for an eighth of a beer”) to establish a pattern as a geometric series.

  30. #30 ObsessiveMathsFreak
    March 10, 2009

    When you are younger, daylight savings time is taught to you as simply the accepted way that things are done. Various arguments are presented as justification and you move one. DST becomes as natural and fundamental as the days of the week or the months of the year. Clearly artificial, but an accepted practice.

    As you get older and start to question things (if you’re the questioning type), DST begins to make less sense. Reflecting on the arguments, you can see why the debate is so obscure. It’s quite difficult to wrap your head around what is going on with all the time shifts taking place. But one fundamental constant doubt should remain in your head throughout.

    You can’t get something for nothing; or There is no such thing as a free lunch.

    The fact that DST never existed before the twentieth century should be a fairly big hint as to its practicality. Societies that came before us, many living on the edge, never conceived of or invented any such system. Their day was tied directly to the sun. They rose when it did, and slept when it went down.

    DST is essentially a product of cheap mechanised timepieces. As clocks became widespread, and timekeeping accurate, people’s days became divorced from the rising and the setting of the sun, and instead revolved around regular clock time. The effect of course was to cause people to rise in darkness and sleep in sunshine, depending on the time of year. So DST was conceived of as a “solution” to this problem, while ignoring the “No Free Lunch” rule.

    It’s useful to examine when DST was first invented. In 1905 by William Willett apparently. By 1905, society had become truly industrialised in its daily schedule, with ubiquitous cheap clocks and timetables determining peoples daily schedules.

    However 1905 was still in the gaslight era. Electrical networks were in their infancy. Street and building lights were still provided in large part by gas lamps. Lighting was expensive, and the regular, industrialised daily cycle had run right into the limitation that had precluded its existence up to this time. People needed daylight to work.

    Hence DST. If Willett had not invented it, someone else in the gaslight era would have, or else something else would have had to give. It was an invention of its time. But Willet was not a scientist, or mathematician. It’s doubtful he fully investigated the consequences of his proposal, and how it could not provide a free lunch. If he did, or if anyone would, they would see that DST giveth even as it taketh away.

    The fundamental problem is of course the artifical nature of time zones. If you live on the same latitude as Greenwich AND are in the same time zone, OR, live an appropriate multiple of 15 degrees longitude AND are in the appropriate time zone, THEN the sun will be directly overhead at in and around noon on each day and you will in theory not need DST. However, outside of these conditions, the sun may be directly overhead at very different times and DST may help or hinder you, but cannot satisfiy you.

    In the modern age, we can rely on electric street and building lighting and are less dependant on the sun for our working day. Moreover, the working day for might begin at 7:00am and end at 6:00pm, or some similar shift, meaning that “working noon” would ideally be at 12:30pm or a shifted hour. And of course, the length of the daily solar day shifts with both season and latitude.

    The bottom line is that fitting a regular clock schedule to the solar day is effectively an impossible problem, with no real solution. We must accept discrepancies between our clock time and our solar day. Measures such as DST are trade offs, which may work for some locations in some timezone, but not for all, and which may not work at the same times. Ultimately it is impossible to get away from the fact that discrete timezones do not and will not ever synch well with continuous solar time.

    In conclusion, I would advocate dropping DST and replacing it with a year round constant time, optimised for the entire jurisdiction, according to appropriate constraints. It would at least be a systematic solution to a difficult problem and not something dreamt up by a gentleman out on his morning walk who did not fully consider the implications of what he was proposing.

  31. #31 Tom
    March 10, 2009

    We physicists tend to be connoisseurs of units, and a constantly changing time standard grates a bit. To be perfectly honest that’s my main slightly quixotic objection to the time change. Opinions?

    But it’s not a change of units. It’s changing the coordinate system — a mere translation in this case — which we physicists do all the time. It’s not even invoking relativistic effects!

  32. #32 Nemo
    March 10, 2009

    Technically, it is “Daylight Saving Time”, not “Daylight Savings Time”.

    Just a little pet peeve.

  33. #33 Roger Sweeny
    March 10, 2009

    Imagine the scientists of the world got together and decided they didn’t like the Celsius degree as their unit of temperature. “It’s silly,” they said, “the scale doesn’t start at a real zero. It’s like starting your length measurements at 273.15 meters. And we don’t say degrees meters. We just say meters. Let’s make a new unit, the same size but starting at zero. We’ll call it the kelvin.”

    And so it came to pass.

  34. #34 CCPhysicist
    March 11, 2009

    I will also point out that your premise about changing units is incorrect: the day has the same length it always has. The change is simply a way to move everyone’s start time without actually changing published schedules.

    If you want to build on the FACTS, look for a book called something like Seize the Daylight, which also explains the origin of our rather odd time zones. Ah, here it is
    Everything is on the web today! He takes it back to Ben Franklin, who liked to sleep in, but the real drive was to get worker schedules to synch with the sun so factories could be lit by the sun coming through the many windows you see in old mills and factory buildings. Saved a lot of money. Reputedly, this remains true today, which is why we extended DST recently.

    Opposition to DST comes from dairy farmers, like an old family friend of ours. They have to time milking to the schedule of processors who deliver it to stores on a DST schedule. In the olden days, it had to match up with the schedule of the “milk train”, which ran separate from commuter trains. Cows didn’t like the change any more than teenagers do.

    I favor a permanent shift. The time zones are nuts anyway, so why not shift them some more? (I grew up in a state where we were 15 minutes from one time zone and 45 from the other, but chose the other to be on Bigger City Time.) Most of us make more productive use of daylight after work than daylight before work.

  35. #35 Paul Camp
    March 12, 2009

    It surprises me how many people have such profound opinions on this subject in the absence of any factual knowledge of the astronomical reasons for it (or even worse, based on folklore reasons like the convenience of farmers in olden days).

    Why would a change be convenient for farmers, or for that matter anyone who works with farmers? The reason is astronomical, not economic.

    The length of the solar day varies, and I’m not talking about long term variations due to tidal interactions, but variations over the course of a year. Most of the apparent motion of the sun is due to the Earth’s rotation, but not all of it. Some is due to the Earth’s orbital motion — about 1 degree per day (360 degrees in 365 days). This contributes about 4 minutes to the length of a day — not much but the changes add up.

    Trouble is they accumulate in a variable way due in part to the tilt of the axis of rotation and to the eccentricity of the Earth’s orbit (according to Kepler, when we are far from the Sun, the orbital motion is slower than when we are near).

    To smooth these variations, we define mean solar time, based on the apparent motion of the sun averaged over a year. The relationship between the two is called the equation of time. When you graph it and fold it in half, you get an analemma.

    Standard time is defined as mean solar time at the center of the time zone. Now how does daylight savings come into play?

    Since standard time is based on mean solar time, sometimes it runs ahead of mean solar and sometimes it runs behind. And this in turn means that when days are getting longer, the extra daylight hours are added on to the beginning of the day whereas when days are getting shorter they come off the end of the day. You can check sunset and sunrise times to verify this.

    Daylight savings time then essentially forces everyone to true up their personal time with apparent solar time. We conduct more of our life in daylight and therefore use less energy.

    Unfortunately, this has become something of a voodoo stick in political circles. It is taken as read that “daylight savings time saves energy” with no real understanding of why. So a cheap and easy way for a pol to demonstrate concern with the Energy Problem is to push extending daylight savings.

    The trouble is that the further you push the ends of daylight savings toward winter, the less difference there is between mean solar and apparent solar time and so the less bang you get for your buck. Right now, it is basically a wash. Any further extensions would probably cost energy rather than save it.

    Our society is so interconnected that, like it or not, you have to synchronize all of society, not just some of it. It doesn’t matter what time we agree on but we all have to agree on it. It is debatable how much energy DST saves — I suspect some but not a lot — but arguments to get up earlier are just DST without DST and arguments to do away with time zones altogether similarly don’t solve anything. People just aren’t going to work the night shift in LA just for NYC’s convenience so without a standard you just go back to random synchronization, which is worse than useless.