https://medicalxpress.com/news/2025-03-naturalness-seasonal-basis-modern-criticism.html
What is the best time to start the day in view of the variation in when the sun rises? This is the problem analyzed by Jorge Mira Pérez and José María Martín-Olalla, lecturers at the University of Santiago de Compostela (USC) and the University of Seville (US), in a study that has just been published in the journal Royal Society Open Science. In it, they analyze the physiological and social foundations of the practice of seasonal time change and review its impact on health.
The study takes as an example the cities of Bogotá and New York, which are located on the same meridian but at different latitudes, to point out that in winter the sunrise is delayed by an hour-and-a-half in the latter city. "This delays life in New York during the winter, but in spring the delay in sunrise has disappeared and activity can start earlier. Putting the clocks forward in spring facilitates this adaptation," says Mira.
The study includes several current and past examples of societies with delayed activity in winter and earlier activity in summer, in line with the synchronizing role of morning light for our bodies. "Modern societies have several synchronization mechanisms. For example, the use of a standard time in a large region, or the use of pre-set schedules. Time shifting is another synchronizing mechanism, which adapts human activity to the corresponding season," says Martín-Olalla. The authors suggest that the first weekend in April and the first weekend in October would be the most appropriate time for the clocks to change.
The study reviews the impact of the seasonal time change on human health, considering two types of effects: those associated with the change itself, and those associated with the period during which daylight-saving time is in effect. In the first case, the authors point out that published studies have not analyzed the problem epidemiologically and that the evidence suggests that the impact is very weak.
"A very comprehensive study in the United States reports a 5% increase in traffic accidents in the week following the clocks going forward in spring but overlooks the fact that from one year to the next, weekly traffic accidents fluctuate by 15%. Changing the clocks has an impact, but it is very weak compared to the other factors influencing the problem," Mira points out.
"Changing the clocks has worked for a hundred years without serious disruption. The problem is that in recent years it has been associated only with energy saving when, in fact, it is a natural adaptation mechanism," says Martín-Olalla.
In the second case, the authors point out that the current controversy stems from an erroneous interpretation of the seasonal time change. According to Martín-Olalla and Mira, changing the clocks is not a time zone jump, nor does it cause the population to live adjusted to the sun in another place, nor does it cause their rhythm of life to be misaligned with respect to the sun.
"In a way it is the other way round, changing the clocks aligns the start of activity with the sunrise," Mira points out. "In 1810, the Spanish National Assembly had already made this kind of seasonal adaptation and there were no time zones or anything like that. Social life is simply reorganized because the length of the day in summer makes it possible to do things in the morning earlier than in winter," says Martín-Olalla.
Mira and Martin-Olalla are highly critical of studies that report long-term effects of seasonal time change and associate it with increased risk of cancer, sleep loss, obesity, etc. They point out that these studies analyze data within the same time zone in the US or Russia, but that says nothing about the seasonal time change.
More information: José María Martín-Olalla et al, Assessing the best hour to start the day: an appraisal of seasonal daylight saving time, Royal Society Open Science (2025). DOI: 10.1098/rsos.240727
(Score: 5, Insightful) by Snotnose on Friday March 21, @01:46PM (3 children)
of the people affected. I want to hear about the rise in auto accidents, heart attacks, and just plain "ooo, it's too early to get up" for the week after the time change.
Face it, any efficiencies are going to be sucked up by wall street, and the rest of us are stuck with the bad parts.
Of course I'm against DEI. Donald, Eric, and Ivanka.
(Score: 3, Insightful) by aafcac on Friday March 21, @02:39PM
If the summary is any indication, this is a bunch of nonsense. Delaying when you do things due to light is quite another thing than delaying everything. I doubt very much that they delayed everything by an arbitrary amount considering that it has only been a few hundred years since reliable clocks were developed and timezones didn't even exist until railroads made them necessary back in the 19th century.
I do think this line of research is somewhat helpful in terms of getting all the angles covered, but it's a crappy basis to make any assertions about what impacts this may have on humans. The way to do that is to compare places that do and don't have this stupid time traveling in the calendar.
(Score: 5, Insightful) by JoeMerchant on Friday March 21, @05:54PM
I believe in "core hours."
If you have a job like retail, with store hours, then sure: the store opens when the store opens and it's good for business to keep that as predictable as possible for your customers.
However, if you're not the one unlocking the doors or other parts of the essential opening and closing staff, do you really need to be on-prem at a specific moment? Wouldn't it make more sense for stocking workers to show up sometime during a +/- 30 minute window, do their job, and leave after their shift hours are done, instead of expecting them to clock in EXACTLY at 8:30AM every day? Staggered breaks are common, why not staggered start/stop times? Shift change traffic at our local hospitals is insane.
In my work, I talk with 4 US timezones + India and occasionally China. Giving all of them a "window of availability" when they can expect to reach me real-time makes sense, but being 100% on-duty every day from exactly when my "shift starts" until when it ends is just crazy on both ends. Our team does two or three (some do four, not me) "morning meetings" per week, since the time change at 10:30AM to accomodate our India based team members who are on the road commuting home at 9:30 now that the US has gone DST (India never does.) We can usually catch our local team members before the meeting, and the ones we can't we can usually catch anytime during the day including a bit after 5pm if necessary, though that's strictly on a mutual agreement basis (like, let's get this done now so I can take the kids to something in the middle of the day tomorrow...)
I would find it much more "socially responsible" for companies to soft-start their shifts with employees arriving at staggered times and with a bit of flexibility so that it's considered 100% O.K. if they show up anywhere within a +/- 30 minute, or more, window. I suppose that puts extra demand on micro-managers who must be present any time any of their underlings are present... and that's why there should be an opening manager who arrives before everyone else, and a closing manager who is the last to leave, and some overlap with both present in the middle.
Some sales-number focused pinheads in Florida want Daylight Savings All Year because they see increased sales during DST. These pinheads don't get up before sunrise, ever, and are probably also screwing up the math on the DST effect vs the naturally longer days during summer at Latitude 25-30.
🌻🌻🌻 [google.com]
(Score: 2) by mcgrew on Sunday March 23, @05:04PM
The time change should be all the proof anybody needs to see that the US is NOT a democracy. 80% or more want the time change gone and have wanted it for decades.
But PLEASE don't make Standard Time the standard! I don't want it getting light at 3:00AM, that's way to damned early! Too dark in the winter for the kids' school bus? Science says kids need to sleep longer so stop starting school at eight o' fucking clock in the morning! The schools shouldn't be open before the hardware stores are! Schools aren't supposed to be a replacement for babysitters.
Impeach Donald Saruman and his sidekick Elon Sauron
(Score: 1, Insightful) by Anonymous Coward on Friday March 21, @01:48PM
I'd write it off if there's 5% reduction when the clocks go back. But is there such a thing?
Otherwise it's still a 5% increase assuming that "comprehensive study" was actually comprehensive unlike this one which just seems to be mainly backed by opinion and handwaving.
(Score: 2) by srobert on Friday March 21, @03:25PM (3 children)
We set the clocks ahead to Daylight Saving Time in the summer. That's backwards. We don't need to save daylight in the summer when there's plenty of it. If we went to DST in winter that would be beneficial to me. I wouldn't have to drive home in the dark. It's the winter where I need to save the daylight for the afternoon. As for driving to work in the dark, it doesn't really bother me. But I've always hated coming home in the dark in the winter. When I was a kid in Indiana we didn't use DST. My sister is still there and tells me that now it's still daylight at 10 PM in June. That sounds awful. But I'm not a university researcher so maybe my opinion just doesn't matter.
(Score: 2) by JoeMerchant on Friday March 21, @06:04PM
I did shift work one summer: 6:30am to 3pm, with a lot of Saturday overtime 5am-10am. Thanks to DST, even 6:30 was deep in the dark for driving, but those 5am shifts were physically insane, as in dangerous. Maybe 10 times in my entire life have I just driven by a turn I was supposed to make and only realized it much later, and half of those times were on those shifts. I also "woke up" pretty far across the center line of the road once or twice on those drives, luckily I never saw another car on the road in that 4:30-5am time slot - which contributed to the alertness problems, but made the drive much safer overall.
Many years later, I had a series of about 8 flights that I took departing the airport one hour drive away from my home at something like 6:20am, so I was leaving the house around 5am - amazingly so much less challenging than 4:30am. At 5-6am on a Tuesday, the freeways were just me and a couple of semi trucks, it was a very calm relaxing trip followed by a breeze straight through TSA. When they shifted the time of that flight to 7:20am there were far too many people driving on MY ROAD, not to mention annoying human interaction at TSA, the lines weren't long yet, but it's not like the entire TSA staff was standing around waiting to serve me, and only me, anymore.
🌻🌻🌻 [google.com]
(Score: 2) by aafcac on Friday March 21, @06:48PM
I think it's because of kids going to school. Most of them are returning home early enough that there's still at least some light. When I was a kid, we got off at either 2:15 or 3:10 depending upon what grade we were in, both of which would get kids home before it got dark. Although, the middle and highschool students would be going to school in the dark. But, with around 8 hours of light at the end of December, there's only so much you can do in terms of shifting the clock settings around.
That being said, the whole thing is pretty stupid, it may have made some sense decades ago, but with the internet and various 24 hour businesses, I don't see any actual upside that comes from changing the time on the clocks when businesses often already have seasonal hours when it makes sense.
(Score: 2) by mcgrew on Sunday March 23, @05:07PM
Which is why DST should be all year long. 3:30AM is too early for the dawn and 4:30PM is far too early for dusk.
Impeach Donald Saruman and his sidekick Elon Sauron
(Score: 5, Insightful) by dwilson98052 on Friday March 21, @04:46PM (1 child)
...to suddenly change the time an hour.
The "researchers" are morons for suggesting this to be the case.
(Score: 2) by Undefined on Saturday March 22, @02:43PM
This is the actual answer. Kudos.
(Score: 2) by Thexalon on Friday March 21, @04:52PM (5 children)
Being in the same time zone as a different area makes it easier to conduct business and trade between them, but with a tradeoff of getting potentially further and further away from the solar time and circadian rhythm of the humans living there.
Because the time zone is tied to trade, that means that who your political leaders choose to match up with often has more to do with who they are doing business with or politically aligned to than it does to what's the nearest 15-degree longitude. For instance, Belarus is on average north and a bit west from Ukraine, but is 1 hour ahead of Ukraine's time zone. Why? Because Belarus decided to match its time zone to western Russia, whereas Ukraine decided to match its time zone to countries on the eastern edge of the European Union. Meanwhile, China could very easily span 3 time zones but decided to make everyone stick to Beijing time even if it means the people in the west of the country don't see the sun until 9 AM.
If you want to read through some of the craziness, the IANA tzinfo data [iana.org] has a lot of the changes described in the comments, along with references to the laws and often very arbitrary changes that end up happening.
"Think of how stupid the average person is. Then realize half of 'em are stupider than that." - George Carlin
(Score: 3, Insightful) by aafcac on Friday March 21, @06:52PM
Keep in mind that the only reason we have timezones is because we developed methods of traveling fast enough that we needed to worry about clocks in large parts of the world. Prior to that, you could just set your clock based on what the sun was doing where you're located and be done with it. Anybody in your area that you'd do business with was either close enough that they'd be on similar time, or so far away that the actual time of day wasn't relevant. But with railroads and now cars, planes, phones and the internet, it's far more useful to know what time it is where you're doing business.
China is also kind of an interesting example where they don't do the clock changing and also stick to one timezone. They get away with reducing 5 time zones to one mainly because of how few people live outside of 2 of those timezones.
(Score: 2) by mhajicek on Friday March 21, @08:44PM (3 children)
I'm sure those who see daybreak at 9am are quite accustomed to it and find it normal and nonproblematic. We could all run on GMT with no DST and do just fine, if people are half smart about setting and changing schedules.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 2) by aafcac on Friday March 21, @09:55PM
The issue with that is when you've got people that are in different parts of the world. Timezones can be kind of annoying, but at least you can set a sort of standardish normal business schedule based in local time rather than having to have different divisions with different hours to make it something sane for the folks in regions that are far away. Having people nominally going to work at 4am, 5,am, 6am, 7am and the like because that comes out to starting at 9am in different timezones is just dumb.
(Score: 3, Touché) by sjames on Saturday March 22, @01:12AM (1 child)
People are but managers (who won't be in till noon anyway) are not.
(Score: 0) by Anonymous Coward on Saturday March 22, @03:38AM