Time questions: Daylight savings and timezones?

Factual Questions
1

Why do we have “daylight savings time” in the summer? The days are naturally longer in the summer. It seems like we should set the clocks forward in the winter so that it stays light an hour later. Can someone explain this to me?

Also, while I am asking time related questions…why did we come up with time zones? Why is it important to have the time of day coordinate with the amount of sun? If it was the same time everywhere on earth it wouldn’t be any different. The people that live on the opposite side of the globe would just have 12 midnight as the middle of their day.
If you fly to the other side of the world now, its not like you just immediately adjust to the time there because of the time zones. You still have to go through jet lag and get used to it. It just seems like it would be a lot easier if it was always the same time everywhere on earth.

2

Yep, if everyone worked during the hours between 8am and 5pm Central Time, it sure would solve the problem of jet lag. I’m not sure how the non-jet set folks in India and China would like it though.

But on to the less ridiculous part of your OP. When you don’t do a DST thing in the summer, you end up with a lot of daylight early in the day, when most people are going to be sleeping. So they shift the time back, so that the sun starts coming up about the time when most people are waking. That gives you even more daylight to use at the end of the day. The idea is that daylight is valuable, and you want to not waste it while people are sleeping.

3

Daylight Saving Time

To the second part of the OP – great idea!!! With no time zones, when someone says “I’ll call you at Noon,” this will make appointments sooooo much easier to remember.

Ah, one problem. What if you live in New York and the person you are calling is in Australia?

4

The original timekeeping device is the sun. Before there were clocks, there was the sun. Noon was always at true solar noon. Then, when clocks were developed, local solar time was still the basis for setting them. Railroads can be blamed for instituting time zones. They needed some sort of standardization of times to prevent crashes and make sure that peopl would know when trains were to arrive and leave. However, they lacked enough political power to force the world onto a single time. Thus, they used “zones” as a compromise. This US and Europe phenomenon was later extended worldwide.

5

I guess that is what I don’t get. It seems like the best way to standardize time would be to make it the same time everywhere. If a train leaves New York at noon and it takes 10 hours to get where it is going then you know it will arrive at 10 O’clock.
CurtC - The people in other parts of the world would not work from 8-5 central time. They would work during the day light hours, but instead of it being 8am-5pm it would just be from some other times. Its all relative. If we work from 9am-5pm, the people on the opposite side of the earth work from 9pm-5am, but they still work during the daylight. The same scheduling problems that exist now would still exist, but instead of having to add or subtract hours to schedule a teleconference with someone in China, you would just have to figure out what time of day falls within the normal work hours for both places.

6

There is a “universal time” where every clock in the world is set to the same time. It’s useful for astronomers, navigators and large international military forces.

For the rest of us, you’re fighting millenia of civilization. “Noon” all over the world is defined as the time when the sun is highest in the sky. With one single time zone, my London office may be open from 9 a.m.-5 p.m., which would make the hours for my New York office 3 a.m.- 11 a.m. and my Tokyo office would actually open at 9:00 p.m. and close at 5:00 a.m. the next morning.

Which might work fine except for two things 1) Human beings have an annoying habit of wanting to sleep at night and 2) there are still a lot of professions in the world that depend on daylight; agriculture, construction, etc., which means the road crews in Tokyo would start working just about the time everyone else is trying to go to sleep.

7

So what problem does that solve? Instead of saying “what time is it in China?” you have to say “How far into the standard work-period is it in China?” That doesn’t seem any easier.

8

Daylight savings in summer: More sun after work when you can use it.

Yes, daylight is longer, but that extra hour provides even more time you can use.

If not for Daylight Savings in Summer, my lawn would never get cut and my car would never be clean. My pool would not see much use either.

In winter, you don’t care all that much because it is too cold in many places to enjoy the outdoors.

I would like two-hours Daylight Savings in Summer.

9

“Just”?

That would be at least as hard, and more confusing to start. Maybe it would be more confusing even after people got used to it, not sure, but that can’t be any better than what we have now.

If companies work 9 to 5 (or like CurtC said, 8 to 5), there’s an extra hour or two on the other side of noon, so it would seem the best solution would be to just work 7 to 3–same number of hours as 9 to 5, but uses the daylight better. Some people would like full-time daylight saving time.

10

We do have a more-or-less universally accepted “world time”: Greenwich Mean Time (GMT), or Coordinated Universal Time (UTC), as it seems to be in vogue to call it now. (OK, I admit I don’t know the story behind the differing names. I’m open to enlightenment.)

I’m not reading the OP in the same manner as some of the posters who have responded. I don’t think it’s being suggested that the whole world adjust its living schedule so that we’re all working or sleeping simultaneously, regardless of the presence or absence of the sun in our local sky.

I think he’s (I’m guessing your gender, horhay_achoa - please forgive me if I’m wrong.) asking why we don’t all set our clocks to UTC, while still scheduling our lives more or less in accord with the sun.

Under this proposed system, the west coast of the US would still go to work, go to bed, etc. some eight hours later than folks in England. We’d just have our clocks set to the same time as Londoners. The “8-5” business day would start at 4:00 p.m. and end at 1:00 a.m., according to our clocks. The sun would be highest in the sky at about 8:00 p.m. - roughly the middle of the business day, and about when we’d be eating lunch. If you didn’t look at a clock, you would never know there had been a change.

The upside to this? As pointed out in the OP, “I’ll call you at 2:30 p.m.” would be completely unambiguous to anyone in the world - all clocks in the entire world would read “2:30 p.m.” at the same time. Since I’m assuming UTC, at this time it would be mid-afternoon in London, and about dawn in Los Angeles.

The downside to this? Pretty much what friedo pointed out. As things currently stand, if I’m told that if it’s 1:30 p.m. in Tokyo, or Kabul, or New York, then I can pretty reasonably deduce that it’s in the middle of the day, businesses are likely to be open, and I’m not likely to be waking my friend up if I call him. IOW, I can do a quick calculation and know pretty much where in the “daily cycle” a given city in the world is.

The proposed system would lose this. The calculation would not be necessary to obtain the “local time” (what clocks say) in Sydney, but since that “local time” (which is simply UTC) has no simple connection to daylight or daily schedules anymore, it’s pretty much useless knowledge.

Neither way is necessarily invalid. But there are tradeoffs involved with both, and for daily living I think the existing system is clearly superior. Like kunilou pointed out, organizations that find the “one-time” method suits their purposes better can and do use it.

11

Not to mention that for some unfortunately timezones the working day would span over two calendar days, making for some awful accounting.

12

Make that “unfortunate timezones”.

13

You can consider GMT to be a time zone (e.g. What’s the difference between PST and GMT?) and UTC to be a time reference (e.g. what’s the current offset between UTC and TAI (International Atomic Time).

There are many different time references that essentially give GMT (UTC, TAI, GPS, UT1, UTC(USNO), etc.) but they have different accuracies and small offsets (whether or not they apply leap seconds, which atomic clocks they use or if they follow the variations in earth rotation, …).
And more on the OP, I think it’s much easier to think “What time is it in Sydney?” as opposed to “How early is it in Sydney at 9pm?”

14

Yes! This is exactly what I am talking about. And I do realize it doesn’t solve anything as far as scheduling or anything is concerned because you would still need to know if it was a time when people would be awake in the other part of the world.

I was just wondering about it. It is interesting to me because time is such a meaningless man made concept, and we have somehow decided that this is the best way for it to be set up, even though it could just as easily be so many other ways. Thanks for the answers!

15

I don’t think we did any such thing. It just happened. Many standards are established without a reasonable consideration of the “best way.”

16

Cecil on daylight savings time: http://www.straightdope.com/classics/a5_052.html

17

Here is the quick explanation. The old system was GMT. There were always 24x60x60 seconds in each day, but the definition of how long is a second was a little flexible.

The new system is UTC, which is Coordinated Universal Time spelled sideways. Each second is precisely defined, and some days have extra seconds thrown in to make up for variations in the rotation speed of the Earth.

GMT and UTC can be off from each other by as much as one second. As far as I know, GMT is no longer used anywhere, UTC being “universal.” However, UTC is often called GMT in non-technical situations.

18

Political reasons come into play. Who gets to have noon be when the sun is nominally overhead?

The French were more than a little peeved in 1884 when it was decided that the prime meridian would pass through Greenwich rather than Paris.

The acronym for Universal Coordinated Time is UTC - an acronym that represents neither the English nor the French. Coincidence? I think not.

19

The acronym UTC was probably selected because there are several UTs and it would make sense to call them, as they are, UT1, UT2, UTC etc. In other words, you have a generic concept of UT and then, if you want to get more specific, you have UT1, UT2 etc.

horhay_achoa you have exactly the right idea about using UT around the world and any objections are just that people are used to doing it differently. If people had grown accustomed to using UT around the world, nobody would have the least problem with it. None whatsoever. Starting the day and having breakfast at 10 pm is as strange as celebrating Christmas in the middle of the summer. In other words, not at all if you are used to it. We are comfortable with Australians celebrating Christmas in the middle of the summer and we would find it strange if they shifted their calendar six months.

Custom dies hard. that is all. If everybody used UT a lot of problems would disappear. Communications networks would not have to keep track of local time differences. Airplanes and trains could directly calculate arrival times without having to account for time differences. Local time makes no sense for satelites in orbit.

It is nonsense to say the present system makes more sense. It makes more sense because you are used to it, that’s all. A man in NY needs to make a call to Europe. He asks “what is the time difference” and he is told Central European time is 6 hrs ahead of ET. That is all he need to know. He knows they will start work 5 hrs before he does and finish work 6 hrs before he does. He would know that he works from 14 hrs UT to 21 hrs UT and that in the west coast they would work from 17 UT to 24 UT. Once you learn that is is very simple and it is better than what we have now. It’s just not going to happen.

20

Just a reminder:

It’s daylight saving time, not “savings”. “Savings” are what you put in the bank.