Daylight Saving Shift
in [Java Programming]
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From: Arved Sandstrom on 2 Nov 2009 22:04 Mike Schilling wrote: > Arved Sandstrom wrote: >> My point was, you can always pin a meeting time to a datetime in *one* >> given location. Phrasing it as a 9 AM Pacific *and* 5 PM British is >> already a cause of problems - just phrase it as 5 PM British *or* 9 AM >> Pacific, and let the other parties worry about the translation. > > Which places the onus on them to figure out that DST has arrived in a remote > country. Not a recipe for success. Not on _them_, leastways not if you mean human beings. That's the whole point of software, to take care of tasks like this. Date and time math, especially if we stick just to the Gregorian calendar, is not exactly that mysterious, even with DST thrown in. The information is available - it's not hidden away. If I'm in Nova Scotia and it's August 2009, and someone in Brussels suggests a meeting at 3 PM their time on Oct 30th of this year, it actually only takes me less than a minute to *Google* up a website that tells me that I'll still be in DST and they won't be...I figure a simple app that talks to a simple database should answer a question like that in not much more time than it takes me to call it up and dial in the info. Because some changes are announced pretty close to the actual switch it's probably most convenient to look up this kind of information from a service. AHS
From: Arne Vajhøj on 2 Nov 2009 22:26 Lew wrote: > Arne Vajhøj wrote: >> Lew wrote: >>> Arved Sandstrom wrote: >>>> Just as for the rules for magnetic declination, I don't even try to >>>> remember any of that. It's easy enough to work out from first >>>> principles and local knowledge. For example, if you know that DST is >>>> intended to give you more hours of light in the evening, that >>>> immediately tells you in what direction the clock must go. >>> >>> The irony is that Daylight Savings does not give you more hours of >>> light in the evening. It just makes people go to (and thus leave) >>> work an hour earlier. The evening itself still has the same number >>> of hours of light. >> >> Not if the evening starts when you are home from work. > > Then when the evening starts depends on what job you do. A farmer's > evening starts at full dark by that definition. > > Doesn't it make more sense to define evening in terms of where the sun > is than what one's profession is? > > I define evening as when the sun is close to setting, i.e., when the > light begins to fade. It's a fuzzy concept, of course, but utterly not > dependent on what the clock says. > > I define afternoon as when sun passes its zenith. > > I find other definitions stupid, as indeed I find the whole concept of > Daylight Savings Time. Ptui! I spit on the practice! Most people follow the clock not the sun. Arne
From: Arne Vajhøj on 2 Nov 2009 22:30 Lew wrote: > Roedy Green wrote: >>> Maybe we will see DST creep till it totally takes over. > > Arne Vajhøj wrote: >> The politicians make that decision. >> >> We just need to write the software to match those decisions. >> >> Note that even if DST changes were completely removed, then we >> would still need to support it due to historical data. > > I would favor abolishing DST altogether. If that means leaving the > clock set ahead of historic Standard Time settings, so be it, although > the last time that was tried in the U.S. (in the 1970s) it was a > failure. People objected to the children having to wait for morning > school buses in the dark, among other things. > > The subject is politically controversial. Some claim energy savings due > to the use of DST. AFAIK there's no hard evidence to support this, at > least, not that takes into account the increase in costs due to air > conditioning and morning lighting. Certainly there are lots of claims > that DST saves energy, but for some reason no one ever seems to cite > studies or methodologies to support those claims. There is a vocal but > politically disadvantaged contingent that denies the validity of those > claims. > > But our infinitely wise and benevolent governments say that it must be > so, though somehow jurisdictions that don't use DST don't seem to suffer > unduly thereby. As Arne points out, dates are a matter of > socio-political mandate and our software simply must reflect the reality. There are plenty of research in this area. References can be found in: http://en.wikipedia.org/wiki/DST#Energy_use http://en.wikipedia.org/wiki/DST#Economic_effects Arne
From: Arne Vajhøj on 2 Nov 2009 22:31 Joshua Cranmer wrote: > On 11/01/2009 10:28 PM, Lew wrote: >> The subject is politically controversial. Some claim energy savings due >> to the use of DST. AFAIK there's no hard evidence to support this, at >> least, not that takes into account the increase in costs due to air >> conditioning and morning lighting. Certainly there are lots of claims >> that DST saves energy, but for some reason no one ever seems to cite >> studies or methodologies to support those claims. There is a vocal but >> politically disadvantaged contingent that denies the validity of those >> claims. > > The recent research summaries I've seen all seem to indicate that the > impact of DST on energy use is somewhere around ±0.2% (it's a number > that's rarely put into full context, so I'm not exactly sure what the > percentage is of--probably average daily summer energy usage). The sign > is naturally hotly debated in political circles whenever tweaking DST is > bandied about. > > *Performs some searching to find research papers* > > The literature review I just finished reading seems to suggest that most > of the conclusions about the energy-saving nature of DST were formulated > about 25 years ago, when lighting in particular was much less efficient > than now (the hypothetical best-case scenario for energy savings would > be equivalent to replacing about 15% of your incandescent light bulbs > with compact fluorescents) and also fails to take into account the > modern shifts in habits. Its primary conclusion was "the stuff out there > sucks, we need modern comprehensive research on this topic." > > Other papers recently published seem to suggest that DST may no longer > be saving energy. That may just be a manifestation of confirmation or > perhaps publication bias--I'd expect that people finding energy savings > due to DST would be less likely to publish their results nowadays. I'm > also not a big fan of DST myself. > > Oh well, if humanity ever discovers interplanetary or even interstellar > travel (as well as sufficiently speedy communication to make > chronological synchronization across disparate settlements necessary), > the mess resulting from DST will be the least of our worries. Wikipedia has lots of references including newer material. Arne
From: Mike Schilling on 2 Nov 2009 23:49
Arved Sandstrom wrote: > Mike Schilling wrote: >> Arved Sandstrom wrote: >>> My point was, you can always pin a meeting time to a datetime in >>> *one* given location. Phrasing it as a 9 AM Pacific *and* 5 PM >>> British is already a cause of problems - just phrase it as 5 PM >>> British *or* 9 AM Pacific, and let the other parties worry about >>> the translation. >> >> Which places the onus on them to figure out that DST has arrived in >> a remote country. Not a recipe for success. > > Not on _them_, leastways not if you mean human beings. That's the > whole point of software, to take care of tasks like this. Date and > time math, especially if we stick just to the Gregorian calendar, is > not exactly that mysterious, even with DST thrown in. The > information > is available - it's not hidden away. If I'm in Nova Scotia and it's > August 2009, and someone in Brussels suggests a meeting at 3 PM > their > time on Oct 30th of this year, it actually only takes me less than a > minute to *Google* up a website that tells me that I'll still be in > DST and they won't be...I figure a simple app that talks to a simple > database should answer a question like that in not much more time > than it takes me to call it up and dial in the info. But if it's a standing 9:00 AM meeting that moves to 8:00 AM for just a week or two [1], the attendees have to know to check. They generally won't. (Yes, calendar software should let you set a meeting to a different Timezone/locale and warn you when repeated meetings change in local time. Absolutely. it should. I don't know of any that does.) 1. Real-life example. |