Talk:Daylight saving time

Maybe I'm staying up too late... :-) ...but isn't this correct also for the Southern Hemisphere? That is, don't you advance one hour in the springtime, whenever spring occurs in your hemisphere? -- Rootbeer

I think so. Spring is always the lengthening of days. In other words, seasons are specific to a hemisphere, but months are the same everywhere. July is a Winter month in New Zealand, as strange as that sounds to northerners! -- Tarquin

It would be correct for both hemispheres, but for the fact that all English speakers in the Southern hemisphere say "autumn" rather than "fall". Except American tourists, of course. :) Tim Starling 04:24 Nov 28, 2002 (UTC)

Usefulness or lack thereof

It has always struck me as odd to "save" daylight in the summer months, when there's so much of it anyway! There are campaigns in the UK to switch to DST all year round, that is to switch to GMT+1, as in winter months schoolchildren walk home around 16:00 and this is just when night falls, the worst time of the day for visibility on the roads. -- Tarquin

Or, they could change the school schedules to a more appropriate time without changing every clock in the country. Am I the only one who thinks daylight saving time is like trying to reduce traffic accidents by recalibrating all the speedometers to make people think they're going faster than they really are? --Brion 02:25 Sep 10, 2002 (UTC)

My comments on this were edited a bit. I originally wrote "Campaigners in Britain would like the country to stay on BST all year round, or to adopt Central European Time". This was altered to read "Campaigners in Britain would like the country to stay on BST all year round, or in other words, adopt Central European Time". But that's not quite what I meant. I meant EITHER stay on fixed daylight saving time all year round, adding one hour to GMT, OR adopt European time, adding an extra hour to winter time and two hours to summer. - Lee M.

Fixed. - Patrick 22:26, 26 Oct 2003 (UTC)

5th Grade Americentric

"5th grade" - this should be changed to an age to be comprehensible to those of outside the USA. -- Khendon

Agreed. -- Tarquin

Usage error?

How is "Daylight Savings Time" not a usage error? It doesn't make any kind of grammatical sense! - Khendon

Does "savings account" not make any kind of grammatical sense? --Brion

Yes, it does. Savings is a noun meaning a fund of money - a savings account is an account of savings. Daylight Saving Time is the Time used to Save Daylight. What does Daylight Savings Time mean? - Khendon

So when the local supermarket offers me MAJOR SAVINGS, it's offering to give me a fund of money over 18 years of age? Daylight Savings Time is, obviously enough to anyone who can parse English, the Time when you make Savings in Daylight. --Brion

re: google searches; it's not enough to do a naive page count. Actually look at the results - searching for the with-s variant turns up many pages saying that the correct spelling is without-s. In any case, who decided any illiterate who can make a web page gets an equal vote? -- Khendon

If an overwhelmingly large portion of the population didn't say it that way, pedants wouldn't feel the need to combat it at every turn. And if "illiterates" aren't enough for you, how about a dictionary (http://www.bartleby.com/61/65/D0046500.html)? --Brion

"savings" are things one stocks and keeps. Unless you're not telling us something, Brion, or should I say Doctor Who!, no-one can make "savings" of time. We are "sort of) saving it in the sense of avoiding its waste. -- Tarquin

That's what makes it so cruelly deceptive -- you may save an hour once a year, but you give it up again six months later. :) I'll point out that, whether "saving" or "savings", there's exactly as much daylight no matter what you do to your clock. You don't save squat. --Brion

"pedants" is it neutral in english ?

Dictionaries aren't authorities on English usage either, Brion; most are overtly descriptive and not prescriptive in nature, and even those that aren't admittedly so are so in practice. All that aside, what's wrong with the present state of the article--it uses the preferred form "saving", and mentions that "savings" is commonly used but often considered wrong. Isn't that exactly what an article on the subject should do? --LDC

Exactly my point, Lee. Yes, the article is precisely correct -- now. Previously it was overtly prescriptive, saying The expression "Daylight savings time" (with the extra s) is a common usage error. One might as well say that "pop" in reference to a carbonated, sweetened beverage is a common usage error which occurs frequently in the Midwest... I'm not sure I've ever in my life heard someone say "daylight saving time" without the s. --Brion

Correct, incorrect. The fact is, the mechanism was originally called daylight saving time, but the only people who care if you say daylight savings time are pedants. A real pedant, me for instance, would say that it should be daylight-saving time. So, except for the tragedy of the missing hyphen, the article is perfectly correct as it stands. Ortolan88

Date of intro in USA

Right now the article seems to state two different dates for the US introduction of DST: 1918 and 1942. Which one is correct?

It turns out both are correct. I've added much more background. -- Minesweeper 09:01 22 May 2003 (UTC)

Note that not every European country observes daylight saving time in the normal sense. Iceland is on constant +1 daylight saving time, which is important during the 4 hours of daylight we get around Christmas.

Anyone know the details of British double summer time (and also I believe German double summer time), that existed for part of the summer during WWII? Mintguy

Time zone source material

I'd like to get a set of rules for major population centers, especially for English-speaking areas (like Japan, where people study ESL).

I want to make some GPL software that tells the user what time it is in his friend or business associate's time zone, taking into account daylight saving time oddities.

Especially when right near boundary conditions, like the last week in March or first week in April, when one might not be sure whether the Other Person is observing the same rules.

I'm going to make the software not only give you the other fellow's local time, but also display whichever rules apply.

So, if I'm in New York and you're in Chicago in the middle of the summer, we're both using the same rules -- so nothing special, you're just an hour behind: my 5:00 P.M is your 4:00 P.M.

But if you're in Indiana, where some counties have opted out of DST...

Or if it's soon after midnight, the last weekend in October and NYC has just set its clocks back -- but you're in Denver and haven't set yours back...

Or Cuba, which "springs forward" an April 1st... or those puzzling folks in Europe who do it a week early each spring...

So, please add all this info to the article, or find me a nice juicy link and all add it myself! --Uncle Ed 16:51, 27 Oct 2003 (UTC)

Nice Juicy Link (TM): http://www.twinsun.com/tz/tz-link.htm -- Catherine 05:03, 1 Apr 2004 (UTC)

Time shifts

...going from 22pm/0/1/2/3am LST to 23pm/1/2/3/4am LDT simultaneously on the last Sunday in March, and back from 23pm/1/2/3/4am LDT to 22pm/0/1/2/3am LST on the last Sunday in October...

Call me stupid, but is there some new system of time we should be using that has 22pm and 23pm, and in which 23pm is equivalent to 0am? What have I missed? - Mark Ryan 04:52, 2 Dec 2003 (UTC)

I fixed the first, but do not understand "23pm is equivalent to 0am": one zone is skipped, because it does not apply. - Patrick 19:48, 2 Dec 2003 (UTC)

22, 23, etc shouldn't be labeled am or pm, should they? The whole point is to avoid the ambiguity of 12-hour clock am/pm-ness.... The 24-hour clock article doesn't explicitly specify but doesn't use them either. Catherine 05:03, 1 Apr 2004 (UTC)

12 hour vs 24 hour again

User 81.225.47.48 changed Brazilian DST starts at 12:00AM of a October (rarely November) Sunday to Brazilian DST starts at noon of a October (rarely November) Sunday in order to be "less ambiguous". True, "noon" is less ambiguous than either "12:00 AM" or "12:00 PM" would be, but is this really correct? Most of the world switches to DST in the night; is Brazil an exception here?? There is no link to a Portuegues article on this topic, and the Spanish version is to brief to give any details. Btw, Brazil stretches over 3 time zones. If all of them change to DST at noon, that must be a mess...

Also, I don't think that going from ends at 2:00 AM on the last Sunday in October to ends at 2 :00 on the last Sunday in October helps "unambiguation". You could argue that such changes does not introduce any new ambiguity, since everybody will understand that the 24 hour clock is used, but my experience tells me that not everybody is used to the 24 hour clock. Aleph4 21:58, 16 Feb 2005 (UTC)

I went ahead and reverted 81.225.47.48's changes. 12:00 AM, although confusing to some, means exactly one thing, midnight.

History of DST in specific areas

I'm familiar with the "rules" of daylight savings time. However, I'm searching for specific answers about its observation in two locations in two different months and years. Can anyone tell me whether or not daylight savings time was observed in (1)Barbourville, Kentucky, USA (Knoxville County) in June of 1950, and (2)Shreveport, Louisiana USA in September of 1954? Or can anyone refer me to a source that has detailed information about which states, counties, or parishes chose daylight savings time during the years when the locals could choose for themselves (i.e., 1945-1966)? Any suggestions would be greatly appreciated.--Miranda Moore

You may want to take this to the Wikipedia:Reference desk, where questions like this are better suited. Dysprosia 03:32, 17 Dec 2003 (UTC)

It's not cheap ($195), but there's a comprehensive book about the history of time changes by locale, designed for astrologers, of all things. (Maybe you can find an older edition on eBay or in used bookstores.) It is available by computer download here: http://astrocom.com/software/pcatlas.php -- Catherine 05:03, 1 Apr 2004 (UTC)

== Sir Sanford Fleming -- first proposed daylight savings time, and not whoever the bloke in the article is. I'm not sure when he did it (sometime in the 1880's) or I'd fix it myself.

He was the one who invented it for the railroads, which ARE mentioned in the article. I'll add him in. -- Catherine 05:03, 1 Apr 2004 (UTC)

Auto safety

Interesting to read about a "spike in the number of severe auto accidents". This is the opposite of the effect I've heard from DST proponents: it's usually claimed that DST saves lives, since many more people will commute during daylight, when it's safer to drive. (Anybody have a source for this?)

Also, the study I found that states that auto accidents spike due to DST (http://www.bnsf.com/media/articles/2004/04/2004-04-01-c.html?index=/media/articles/index.html) says that auto accidents dropped by the same amount when daylight savings ends (and people get extra sleep). So making a spike in auto accidents sound like a simple case-against sounds quite misleading.

DST

Can someone tell the server about a phenomenon called Daylight Savings Time, so I don't have so switch between GMT-5 and GMT-6 every time we have DST?

The specific date, direction, and amount of shift to "correct" for the changing light levels is very much location-specific; indeed, some places don't have any need of it at all. The server is in GMT (well, an approximation of UTC-1, AIUI); the clocks change but twice a year, and I'm sure that you can cope. In fact, I don't have it change, and use my head to do the offset instead (well, 'tis only an hour for me, so...).

James F. (talk)

It would be simple. There could be a check box that says "Please auto-correct my time shift for daylight savings time", so it would only do it if you wanted it to. If there are different types of daylight savings times around the globe, it could have an option to select which type. Worth submitting a feature request for, I might do it soon if nobody else has. —siro χ o 04:26, Aug 2, 2004 (UTC)

Over here in Israel, there is a vote taking place every year, that determines the DST shift in/shift out. Computer modelling of our politicians to predict what they are going to vote on would be mostly welcome. :-) Seriously, a common practice is using NTP to feed off a trusted server, and once it jumps, you know that the daylight savings jumped. The server is manually updated. Some systems just have some hardwired approximate default dates, so around the shift they give wrong time for about a month in the worst case. BACbKA 20:58, 2 Aug 2004 (UTC)

You use NTP to transmit local times and not UTC? Oh, the horror, the horror... David.Monniaux 14:07, 8 Aug 2004 (UTC)

Israel appears to define the start of DST in the common calendar and the end by the Hebrew calendar, which actually makes sense. Because of a Sunday to Thursday workweek, Israel starts and ends Friday. Henry Troup 22:09, 5 Apr 2005 (UTC)

Most open source Unix systems use a library produced by NIH that knows about virtually every set of timezone rules on earth and is capable of translating things like US/Eastern + an offset in GMT into the local time and date. This library is extremely well maintained, the timezone files cover almost all jurisdictions on the planet, and updates come out several times a year. The code is all open source. There is no reason not to use it. --Pmetzger 21:03, 3 Aug 2004 (UTC)

Xerox timezone converter app is down

The link Time Zone Converter (http://sandbox.xerox.com/stewart/tzconvert.cgi) is down as of 4 November 2004. I have hidden the same in the article. --Mahadevan T S 10:44, 4 Nov 2004 (UTC)

So how exactly is DST useful ?

Can the article have some statistics or have a link to some statistics that list out the sunrise and sunset times of major countries, for different months of the year. I live in the tropics, and haven't experienced DST. Hence its difficult for me to understand exactly how people (in the temperate zone) find DST useful and how it affects their daily life. Jay 10:05, 18 Feb 2005 (UTC)

I've lived in Hawaii most of my life (with no DST) but went to school in the U.S. Pacific Northwest, which is around 45 degrees north latitude. That far north, sunrise usually happens at around 05:00 (DST) and the sun sets at around 21:00 (DST)...that means that you could go for an evening stroll while it's completely lighted. I'm sure there are some calculators around that allow you to calculate sunrise and sunset given latitude and longitude... KeithH 07:28, 25 Mar 2005 (UTC)

The big advantage of DST is that it "transfers" an hour or so from early in the day when few people are up and about to the evening, when activity is high. In effect there is a "free" hour of sunlight, with consequent savings in electicity usage. During WW2 the UK experienced double DST, when the clocks were advanced two hours rather than one, to take advantage of the very long hours of sunlight in high summer. Personally, I enjoy the long summer evenings, and it is pleasant to take a stroll or have a relaxing drink outside at that time of year, using time that would otherwise be dark. A disadvantage for parents of small children is that it can be harder to get them to sleep while the sun is still quite high in the sky. Pete 08:55, 23 May 2005 (UTC)

I challenge a statement made in the main article

Some campaigners in Britain would like the country to stay on British Summer Time (BST) all year round, or in other words, adopt Central European Time and abolish BST. … This would make winter evenings longer, thereby reducing traffic accidents and cases of seasonal affective disorder.

It wouldn't necessarily reduce SAD. I suffer from it, and for me the biggest problem is the darkness in the morning. Many SAD sufferers, including myself, need the dawn to tell our bodies that it is time to wake up and hence have difficulty waking up during the winter. We can also have difficulty staying awake during the day as, even though we may have had eight hours as recommended, our bodies are still convinced that we were woken up in the middle of the night.

Granted, the above problems can be worked around with a dawn simulator, but that does not excuse adopting a time system that would trigger new cases of SAD and/or worsen existing ones. The existence of a treatment for any given illness does not make it ethically acceptable to adopt an avoidable practise which will trigger that illness, and SAD is no exception.

Melatonin is produced as it gets dark, making us feel sleepy. At dawn, as the light increases, melatonin production falls and we start to wake up. We find it difficult to wake up on dark mornings because our melatonin levels are still high.

From: http://www.lumie.com/sad.htm

Other information: http://www.solar-components.com/dawnsim.htm

(Please sign your posts on Talk pages using "~~~~") But what do you disagree with? It says "some campaigners" and it says the number of cases of SAD would be reduced. Not you, perhaps, but some. Paul Beardsell 01:13, 19 Feb 2005 (UTC)

Saving/savings and such confusion

I suspect that hyphenating the title would make it more obvious as to what everything means; "daylight-saving time". porges 09:57, Mar 21, 2005 (UTC)

Sir Sandford Fleming

Does the paragraph on Sir Sandford Fleming belong in this article? I don't think so. He was involved in the creation of "standard time", i.e., time zones, but he didn't have anything to do with daylight saving time. Indefatigable 23:40, 25 Mar 2005 (UTC)

DST Errata?

What technically applies to bars and television schedules?

For instance in the fall, what do clocks jump to when it turns 2am? Do they go to 1am?, or do the clocks go from 2:59 to 2:00? What happens to broadcasts for this extra hour (besides the pragmatic answer of "infomercials"). What about bars? They variously seem to stay open an extra hour, lending credence to the former conclusion that clocks go from 1:59am to 1:00am, then resume normal progression.

What happens in the case of the jump in spring, from 02:00 to 03:00? Do the clocks go from 01:59 to 03:00? As interesting as the thought exercise is, I had much better things to do than staring at a clock to figure this out. Also, I didn't realise it was DST in order to look (I noticed my alarm clock was an hour and 10 minutes behind my computer clock, instead of just 10 minutes).

Is there a "universal time" such that no time zones or DST effects occur? Something like computers do with "Seconds Elapsed since 1970". I can see such a thing being extremely critical in time sensitive calculations such as astronomy. I realise astronomers usually don't care about to-the-second accuracy, but to-the-hour accuracy makes more sense, and in the context of DST, that's precisely where the inaccuracies occur. This is illustrated by me asking what happened 48 hours ago at 1am on Month 3rd, and it just became DST on Month 2nd. I probably mean an absolute 48 hours ago, which would be 1am of Month 1st, not at 12am of Month 1st. If I were simply running calculations based on a clock, not realising or figuring in for DST, this accuracy would crop up (I'd be determining what happened 49 hours ago, not 48 as required). However, this error does cancel out if the time interval crosses the boundary from DST to Standard again. There's also some question of what kinds of errors occur when times involved fall right on these boundaries, particularly when the boundary points are at the ends of the time interval. It almost seems like the sort of ambiguity that occurs when a programmer has to make an arbitrary decision about something.

Have DST to Standard time boundaries every caused any actual problems in the real world, besides people not getting enough sleep and getting into car accidents or not doing well at work?

As far as traffic safety goes, personally, I'd come to the knee-jerk conclusion that night driving is safer than daytime. My rationale is very simple, so simple you'd say "Well, why didn't I think of that?" or the ever-perrenial "I could have thought of that."

Rationale: There's less traffic on the road at night, leading to less vehicle-vehicle collisions. This is especially true in less populated areas, but also somewhat applies in large cities as well. Of course, this neglects the problems of drowsy drivers running into more stationary objects, particularly by the ever-present collision spike around 02:15, when the drunks are kicked out of the bars (whether or not they're fit to drive) by law. Of course, if you're a night-owl like me, night driving doesn't pose much of a problem. Of course, gas being as pricy as it is now, I don't even do much driving anymore, when I can help it. JD 09:07, 3 Apr 2005 (UTC)

Daylight Saving Time at WebExhibits (http://webexhibits.org/daylightsaving/b.html) and About Daylight Saving Time (http://www.timeanddate.com/time/aboutdst.html) address some of your questions.

The "universal time" without time zones or DST is indeed Universal Time, also known as Greenwich Mean Time, more particularly Coordinated Universal Time. But the latter does have leap seconds that seem to interrupt the normal flow of clock time having only 60 seconds per minute, due to Earth's slowing rotation (23:59:59 → 23:59:60 → 00:00:00 UTC). — Joe Kress 00:02, Apr 4, 2005 (UTC)

Queensland

Queensland did in fact experiment with DST, for 1 or possibly 2 years, in the late 1960s or early 1970s. I know because I lived there at the time and it was very topical. The then Premier Sir Joh Bjelke-Petersen decided not to repeat it after then. The story goes that his political supporters, a large proportion of whom were rural dwellers, did not like DST because "the cows get confused and don't produce enough milk", or "the extra sunshine fades the curtains". These are no doubt apocryphal, but still say something about the kind of people we're dealing with here. Queensland has therefore been out of step with the rest of the eastern seabord for 35 years (some would say forever). JackofOz 04:43, 11 May 2005 (UTC)

I lived in Queensland at the time, and thought that it meant I'd get an extra hour to lie in bed of a morning and read. Boy, was I wrong!

The reason it was dropped wasn't political but geographical. Queensland is one of the more decentralised States, and consequently a large percentage of the population lives north and west of the capital city of Brisbane, which is at the extreme south east corner of the State. With the Tropic of Capricorn only a few hundred kilometres north of Brisbane, a large amount of the State is in the tropics where the benefits of Daylight Saving are minimal. The coastline trends north-westerly, exacerbating the problem the further north one goes. Residents of Mount Isa, for example, found that in summer they were having to get up before dark, and schoolchildren were walking home during the hottest part of the day. There was little benefit in it for a great many Queenslanders, and rather than divide the State into two time zones, the scheme was dropped. It must be remembered that Tasmania, the southernmost State, begins DST earlier and ends later than the mainland States, and that the permanent difference in time zones between (say) Victoria and South Australia causes no problems. Pete 09:06, 23 May 2005 (UTC)

DST in Winter

I've long thought that in a hot and sunny country like Australia, we should have DST, but rather than doing it in summer, we should do it in winter instead. Australia is already way too sunny, as evidenced by the highest rate of skin cancers in the world. We simply don't need any more daylight in our lives in summer, we have too much already. But in winter we could definitely do with some more daylight at the end of the day, whereas currently we tend to go home in at best fading light, or more usually darkness. Yes, it would mean we'd be getting up in darkness, but that's true for most people anyway so there's no loss there. I've been on this particular soapbox for at least 30 years, but so far our governments have failed to heed my brilliant advice. JackofOz 04:43, 11 May 2005 (UTC)

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