In today’s beemail Dr Reeves says DST does “induce a critical mass of people to shift their activities earlier in the day so as not to waste so much daylight by sleeping in hours past dawn.”

For me this seems to be backwards. Sunrise on Oct 31 was 7:14a, and Nov 1 was 6:15. I generally wake up at 8am - so I slept through 46 minutes of daylight on Oct 31 and 1 hour 45 minutes on Nov 1.

(In a similar vein, sunset on Oct 31 was 6:03p but on Nov 1 was 5:02p, so I also think the evening was shorter - and so any “after 5” club sports would have only 2 minutes of daylight after Nov 1!)

Am I missing something?



This is because we moved from Daylight Savings Time to Standard Time this last week (in most parts of North America). So you were in DST when you were only sleeping through 46 minutes of daylight and it’s Standard Time that now has you sleeping through 1h 45m of it on the 1st and the sun setting at 5:02 PM instead of DST’s 6:03 PM.

(Unsolicited opinion: Permanent DST gets :+1: :+1: from me)

Yeah, @mary nailed it. My argument (reproduced below in case you missed it) is about why to make the clocks spring ahead in the spring. The reason to make them fall back again in the fall is so that sunrise doesn’t end up way too late in the morning (for us here in Portland it would be close to 9am at winter solstice if we did permanent DST).

I also heard lots of objections along the lines of lost productivity and increased traffic accidents caused by the time change. Those arguments could persuade me! But they’re not necessarily dispositive. Like I say below, having more time for evening activities in the summer is a big deal! And shifting all the existing schedules and meeting times is not remotely tenable.

(The point was further driven home for me today when I briefly considered proposing to friends/colleagues that if people preferred, we could move a regularly scheduled thing an hour earlier to keep it at the same body time. I then immediately realized that was more trouble than it was worth and of course it should just remain at its scheduled clock time. So if anyone still has the idea that we don’t need to change the clocks in order to save that daylight, I’m pretty confident you’re wrong! Whether it’s worth it to save that daylight is another question.)

Mainly I’m delighted by how sane the debate has gotten, with everyone acknowledging the various tradeoffs. My impression in the past was that people mostly treated DST as something profoundly idiotic that had literally no conceivable justification! Maybe my (counter-)ranting about this every year finally worked?

UPDATE 2022: No, here’s an example of the standard rant. I guess it’s just my social circles that are getting saner.

Here was the daily beemail in question.

Permanent DST gets :-1::-1::-1: from me. It’s massive discrimination against evening people, forcing most people to get up while it’s still dark (which in my unscientific opinion is totally unnatural, and in my regular opinion is just plain awful) for part of the year.

I’d personally be fine with permanent non-DST, but I’d settle for moving it back to where it was before Congress repeatedly decided to create a few more weeks of misery every year.


I feel as though there wouldn’t be much actual difference between switching to permanent dst or non-dst. The specific numbers are arbitrary constructions, especially if they’re stuck in place. “Evening” is just whenever the sun starts to set.

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I disagree. There are strong cultural expectations about what “business hours” are. Jobs that are currently 9-5 would continue being 9-5 whatever 9-5 actually is in terms of the sun.


I think the right concept handle for this is body time.

Brilliant! Thanks for sharing, etc.

Experience of DST varies wildly, particularly according to latitude. Obvious arguments in one place are often absurd in another.

And you’re a week late. The Aussies will have another view.

Took a while for the cat-who-lives-with-us to adjust to us feeding him an hour differently. Body time for the win!

Daylight Savings Time is a brilliant (mad)hack solving an otherwise utterly intractable coordination problem.

People adapt to all sorts of business hour weirdnesses. e.g. late opening (or entirely closed) on Sundays. In the UK it’s often early-closing on a Wednesday and late-hours on a Thursday. Folks will cope.

e.g. Beeminder could set office hours and the world would adapt. You want help? We’re open this hour on alternate Thursdays. Soup Nazi rules. Nanny bee knows best.

If many businesses were to not start opening until solar noon, shopping patterns would adapt. The coordination roughly takes care of itself, workers in those businesses might self-distribute across more time, reducing rush-hour pressures, etc.

shift their activities earlier in the day so as not to waste so much daylight by sleeping in hours past dawn.

Farming communities, of course, run by daylight in any case, whenever possible. The entire province of Saskatchewan doesn’t change time, for instance. Neither does India, and it’s pretty big. The nearer you are to the equator, the less sense it makes. And of course there’s bits of places that do and don’t adhere to it – iirc there’s a roughly concentric chunk of Arizona that does/doesn’t/does adhere to the general North American rule.

There’s also massive weirdnesses like Spain, where they’re officially on the same time as Germany for co-ordination/loyalty purposes, but in practice run their meals and siestas more according to body time.

Sure, it makes life a living hell for computer programmers.

I only learned relatively recently that there’s an API for that. Tracks daylight savings conversions by date and lat/long location. Conventional wisdom is that in any application that matters (e.g. data warehousing) you need to store both local time and some absolute timestamp.

As for transport, with a smoothed notion of rush hour, more trains etc available at various times, enabling more spread rather than more concentration.

And the brilliance of the Coronavirus! Oh my goodness, what a leveller. Work from home, etc. https://www.youtube.com/watch?v=E4F-pXvLWk4

And the idea that people could just choose on their own to wake up earlier when the days start getting longer is all wrong. I mean, yes, you can personally do that, but it does you no good unless everyone else (like the rest of your ultimate frisbee team) does it too.

Gosh, I was blessed in my last proper job. Almost never ever used an alarm. Woke up when I did, made my way to the office, etc. Expected my team to do the same. That’s what daybreak is for.

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I’m not right convinced by this “extra daylight in the evening” argument. It might be a matter of latitude. Here in the north of England (at 53.6°N) our daylight times just after “fall back” are 06:52-16:47 and just before “spring forward” they are 05:49-18:46. The only bit of “winter time” where we get any “evening daylight” at all outside the 9-5 window is from ~7 Feb to ~28 Mar (about 7 weeks). And we would have some post-5pm winter daylight up until ~21 Nov (another 4 weeks) if we didn’t abruptly steal it by putting the clocks back. I’m not sure why in midwinter it’s somehow more acceptable that it’s it dark before 4pm than it being dark at 9am given that it is a 9-5 world.

(And what I really don’t understand is why the clock changes, if you are going to have them, aren’t symmetric with respect to the solstices? I remember being in France one September in the 1990s and the clocks went back then, which was weird to me at the time but more logical than waiting until the end of Oct once everything got standardised across Europe in the 2000s. (Actually I don’t know when the French put them forward then so they might not have had greater seasonal symmetry I guess.))


This is delightful and I obviously have strong opinions about it.

Sunday marked the return of what in our house we call “real time”. This is because solar noon should occur when the clock says noon. Anything that messes with that, including daylight savings time, is a crime against reason and humanity.

And yet… unless you live pretty much in the middle of your time zone, this doesn’t happen even during Real Time (Denver is actually directly on the 105th meridian, which I know because I was walking through the train station there one day and noticed a plaque on the ground with a line marking it).

And even if you are situated directly in the middle of your time zone, solar noon varies throughout the year, sometimes by several minutes from Mean Solar Time.

Now you might think that as a programmer I could see how arbitrary it is that we say 12:00 is equivalent to solar noon, when we could just as easily say that it should be at 1pm, making “solar midnight” 01:00 instead of 00:00. It’s the difference between a 0-indexed array and… a 1-indexed array, which is obviously terrible.

So the “permanent daylight savings time” solution is already terrible on two counts (it uses 1-indexed arrays and makes solar noon an hour off, on average, from clock noon).

The third nail in the coffin is that not accounting for the change in daylight hours throughout the year is batshit stupid as soon as you get past the Tropic of Cancer/Capricorn. I used to think that people could just get up when they wanted, and if it meant I could enjoy four hours of sunlight, alone, on a trail in the morning because I had gotten up with the sun at the “ungodly” hour of 4am on the summer solstice, then that was totally fine. But I think the intractable coordination problem outweighs that since it gets the point across to the general populace that “hey you should probably listen when your body is telling you to wake up earlier because the sun is up”. Sweeping generalization? Totally.

The abrupt shift causes problems, obviously (apparently it literally kills people). So I would be in favor of the system you mention, where the day starts at sunrise and all references to time are indexed to that[0]. Which would actually get computer programmers out of their living time zone hell, because it would be laughably absurd to try to account for all the different time “zones” and so we’d all just give up and use UTC whenever we needed a … wait for it … universal coordinated time.

I obviously have zero hope that that would ever happen, and I think if anything changes it would likely be in the direction of Permanent Daylight Savings time, so I look forward to being the old man yelling at the kids to get off my damn lawn because it’s 9am in December, and we’re trying to sleep over here since the sun doesn’t come up for another four minutes.

[0] This is apparently what they do in Kenya (or did before colonists came along), but I can’t find a link so it’s just based on what I heard from people there.


Found some history to understand why it started (WWI)… there’s also sections for American and European history. Seems it doesn’t save energy anymore, but causes health problems…I think keeping standard time in the summer but reversing dst (1 hour forward in November) might make some sense

My understanding is that everyone based time on the sun until the advent of the steam engine, at which point it became impractical for scheduling transit between many stations, since each station would have its own time under the old system, and so timezones were invented.

I don’t know the answers to these important and pressing questions, but if it was not just a boring practical decision about office hours and tractors, maybe it’s something to do with the “equation of time”? https://en.wikipedia.org/wiki/Equation_of_time

I don’t remember anything about it except once being in a physics lecture about it. Wobbly things hanging in space may not be fully symmetrical, should not be used as a substitute for a varied diet, etc.

Actually I think I do remember being told it (eqn of time) is related to this: As you may already know, here in London for example, the earliest sunset happens on the 13th of December, almost three weeks before the latest dawn (either 31st Dec or 1st Jan, dawn is the same time same within a second on those two days). And the shortest day is on the 21st of Dec, which is not in the middle between those two dates. That’s not a matter of bureaucracy!

I heard the same story… it does sound a bit pat doesn’t it? Is reality ever that simple? If even I know how it’s supposed to have happened, it can’t possibly be true.

If you’re right, but the studies are correct that DST does kill people and messes with our sleep causing all kinds of medical harm, do we have to choose between massive discrimination against evening people and and massive discrimination against morning people?

I don’t know the answers – this isn’t rhetoric, nor a rhetorical question come to think of it

Also, is there actually such a thing as “evening people” or “morning people”? I know this is a very popular notion, and people often self-identify as one or the other, but I’m genuinely curious whether there is evidence to support the idea that some people naturally like to wake up or go to sleep earlier/later than others relative to the sun.

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IMO society is already extremely slanted towards those who like to get up early (seriously, it’s not natural to get up before dawn, that’s why most people have to use this invention called an “alarm clock” to do it), so no, we just have to make a reasonable compromise.

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