DST (dayligt saving time) rules update

R

Roedy Green

Get http://java.sun.com/javase/tzupdater_README.html

Sun DST Timezone updater: update all your current and obsolete
JDKs/JREs to latest DST/timezone tables. DST globally is not as simple
as in North America. The rules vary over time and by jurisdiction.

DST ends in North America on 2009-11-08.

--
Roedy Green Canadian Mind Products
http://mindprod.com

On two occasions I have been asked [by members of Parliament], "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
~ Charles Babbage (born: 1791-12-26 died: 1871-10-18 at age: 79)
 
R

Roedy Green

Sure about that??

you are right, 2009-11-01, 1st Sunday in November, starts second
Sunday in March.


I am just about to add DST start and end to the holiday calculator.

For hints on what to do to ensure a smooth transition, see
http://mindprod.com/jgloss/dst.html

--
Roedy Green Canadian Mind Products
http://mindprod.com

On two occasions I have been asked [by members of Parliament], "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
~ Charles Babbage (born: 1791-12-26 died: 1871-10-18 at age: 79)
 
R

Roedy Green

I have a hard time swallowing the idea that DST is simple in North
America. Unless one considers that Indiana is not in North America:

Circa 1976 I got interested in how to compute the motions of planets
and moons. That lead to learning about civil time. When the notion
of DST was first introduced, it was called "war time". It had up to a
5 hour shift. It was introduced in a complete patchwork, reminiscent
of the way ancient Romans could bribe to have days inserted in or
removed from a given month.

I would be surprised if Sun attempted to track all that early lore.

Today's rules are "simple" by comparison.

I think DST was a goofy idea. Leave the time alone. Just open
businesses earlier.
--
Roedy Green Canadian Mind Products
http://mindprod.com

On two occasions I have been asked [by members of Parliament], "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
~ Charles Babbage (born: 1791-12-26 died: 1871-10-18 at age: 79)
 
A

Arne Vajhøj

Roedy said:
Circa 1976 I got interested in how to compute the motions of planets
and moons. That lead to learning about civil time. When the notion
of DST was first introduced, it was called "war time". It had up to a
5 hour shift. It was introduced in a complete patchwork, reminiscent
of the way ancient Romans could bribe to have days inserted in or
removed from a given month.

I would be surprised if Sun attempted to track all that early lore.

Today's rules are "simple" by comparison.

I think DST was a goofy idea. Leave the time alone. Just open
businesses earlier.

That does not change the fact that all of North America does
not have the same DST rules.

Arne
 
A

alexandre_paterson

I have a hard time swallowing the idea that DST is simple in North
America. Unless one considers that Indiana is not in North America:http://en.wikipedia.org/wiki/Time_in_Indiana


In particular, rules changed in USA (and Canada) in 2007.

On this 2007 rules changed subject...

From the Joda-time FAQ (first FAQ):

"Does Joda-Time support the 2007 US and Canada time zone rules?
"
"The time zone rules occur in three key places, your operating
"system, the JDK and Joda-Time. To be sure of hitting no issues,
"you should ensure that all three of these have been updated.
"
"Version 1.5 of Joda-Time contains all the daylight savings rule
"updates for the 2007 US change.

Joda-Time is arguably a much better date/time abstraction than
what was available by default in Java so...
 
D

Dr J R Stockton

In comp.lang.java.programmer message <2ce7c5lree86gs7o8h3iph2acdhd8gttuf
@4ax.com>, Wed, 30 Sep 2009 13:10:37, Roedy Green <see_website@mindprod.
com.invalid> posted:
Circa 1976 I got interested in how to compute the motions of planets
and moons. That lead to learning about civil time. When the notion
of DST was first introduced, it was called "war time". It had up to a
5 hour shift.

Have you evidence supporting a clock change, possibly stepwise, making a
five hour difference? Where?
 
D

Dr J R Stockton

In comp.lang.java.programmer message <[email protected]
That does not change the fact that all of North America does
not have the same DST rules.

Firstly, you have to define North America; Mexico and southwards
including Cuba change their clocks variously differently; Greenland uses
EU rules, of course, and therefore changes on Saturdays (they are quasi-
Danish).

All of the USA has, by law, the same rules for the allowable clock
change date/times, but parts do not make those changes.

Canada decides by Provinces, and so has several sets of rules, most but
not all of which match each other and those of the USA. Most of
Saskatchewan, and some other parts of Canada, have no Winter Time.
Newfoundland and Labrador change clocks on the same day but at different
times.

See <http://en.wikipedia.org/wiki/Daylight_saving_time_around_the_world>
and links.
 
R

Roedy Green

Have you evidence supporting a clock change, possibly stepwise, making a
five hour difference? Where?

This was in the USA I think it was in the 1930s. It was called "war
time". I don't know which war they were referring to. Individual towns
could decide to institute it as they saw fit.

I read about this circa 1976, so the details are not fresh.

--
Roedy Green Canadian Mind Products
http://mindprod.com

There is one brain organ that is optimised for understanding and articulating logical processes, and that is the outer layer of the brain, called the cerebral cortex. Unlike the rest of the brain, this relatively recent evolutionary development is rather flat, only about 0.32 cm (0.12 in) thick, and includes a mere 6 million neurons. This elaborately folded organ provides us with what little competence we do possess for understanding what we do and who we do it.
~ Ray Kurzweil (born: 1948-02-12 age: 61)
 
M

Martin Gregorie

This was in the USA I think it was in the 1930s. It was called "war
time". I don't know which war they were referring to. Individual towns
could decide to institute it as they saw fit.
Here's some American daylight saving history

http://www.webexhibits.org/daylightsaving/
congressionalResearchService.html

which seems quite definitive, and a little more detail about other
countries here:

http://www.webexhibits.org/daylightsaving/e.html

There's no mention of any 5 hour timestep though.
 
R

Roedy Green

There's no mention of any 5 hour timestep though.

I had a look too. The best I could find was
http://java.sun.com/javase/timezones/
that said "usually one hour" implying other offsets.

and a National Geographic site
http://news.nationalgeographic.com/news/2009/03/090305-daylight-saving-time-facts-history.html
that said it was a "crazy quilt" of offsets and start/end times prior
to standardisation.

In 1985 I gave away everything I owned but a suitcase. Among the
things I gave away was the book that talked about the early history of
DST. I recall it had a pale blue cover. It was probably quite an old
book. I recall imagining the author would have been some stuffy,
elderly English gentleman with flowing white hair and beard.

Every record has been destroyed or falsified, every book has been
rewritten, very picture has been repainted, every statue and street
building has been renamed, every date has been altered. And that
process is continuing day be day and minute by minute. History has
stopped. Nothing exists except the endless present in which the party
is always right.
~ George Orwell 1984

One distressing thing about the Internet is most links go stale within
seven years, especially about current events. We are deliberately
erasing our history, at least partially.

It would be better for everyone if there were no websites, just
documents floating about on caching servers and end user machines
digitally signed and duplicated as needed. They could not be revoked,
just replaced. But that would make the Internet a completely level
playing field in terms of bandwidth, so the idea will not likely sell,
at least not until the cost of bandwidth drops considerably.




--
Roedy Green Canadian Mind Products
http://mindprod.com

When you can’t find a bug, you are probably looking in the wrong place. When you can’t find your glasses, you don’t keep scanning the same spot because you are convinced that is where you left them.
~ Roedy
 
M

Martin Gregorie

One distressing thing about the Internet is most links go stale within
seven years, especially about current events. We are deliberately
erasing our history, at least partially.
Boy, ain't that the truth? For some years now I've made private copies of
stuff that I think may get revised or 'lost', but it doesn't just apply
to the 'net. I'm currently re-reading "Winged Victory by V M Yeats for
the 3rd time. It is reckoned to be the best WW1 flying novel and one of
the very few WW1 flying books that WW2 aircrew would read. The second
time I read it noticed that an alleged complete text was missing a
chapter I remembered from the first time. I'm interested to see if this
copy, also said to be complete, has it.

However, I digress. I remember, back in the late '90s, reading the Debian
date and time database for the UK. That's the database that records when
calendars and time standards changed. Back then it still a huge, heavily
annotated text file whose comments often included the text of e-mail
discussions about historic calendar changes and esoterica suck as whether
even regional time of day had a valid meaning before the railways came.
It was a fascinating read and I wish I'd kept a copy because its
apparently vanished in a puff of tachyons. I've looked for it a few times
but without success.
 
A

Arne Vajhøj

Roedy said:
This was in the USA I think it was in the 1930s. It was called "war
time". I don't know which war they were referring to.

US was not involved in any wars in the 1930's.
Individual towns
could decide to institute it as they saw fit.

It does not fit with the story at:

http://en.wikipedia.org/wiki/Daylig...ed_States#History_of_DST_in_the_United_States
I read about this circa 1976, so the details are not fresh.

I believe that.

Arne
 
R

Roedy Green


I found another reference to 2-hour shifts:

Clock shifts are usually scheduled near a weekend midnight to lessen
disruption to weekday schedules. A one-hour shift is customary, but
Australia's Lord Howe Island uses a half-hour shift.[25] Twenty-minute
and two-hour shifts have been used in the past.

http://www.answers.com/topic/daylight-saving-time


Germany then Britain had DST during WW I.


according to
http://voices.washingtonpost.com/rawfisher/2009/03/its_time_for_double_daylight_s.html
FDR called daylight time "war time."


according to

http://www.timeanddate.com/news/time/uk-debates-to-extend-dst.html
However, there were periods, especially during World War II, when the
start and end dates were altered or more substantial clock shifts were
made.
(This refers to Britain, not the USA. This is probably what I recall
from the alleged blue book, after all Britain and the USA are both
foreign countries,separated only by language.)

according to
http://www.timeanddate.com/news/time/france-spain-summer-time.html
France and Spain have peculiar form DST informally called Double DST.
--
Roedy Green Canadian Mind Products
http://mindprod.com

When you can’t find a bug, you are probably looking in the wrong place. When you can’t find your glasses, you don’t keep scanning the same spot because you are convinced that is where you left them.
~ Roedy
 
D

Dr J R Stockton

In comp.lang.java.programmer message <j5tec55mi3om8f407vdf2uimi7u4ce9006
@4ax.com>, Sat, 3 Oct 2009 09:15:54, Roedy Green <[email protected]
om.invalid> posted:
It does not fit with the story at:

http://en.wikipedia.org/wiki/Daylight_saving_time_in_the_United_States
#History_of_DST_in_the_United_States

I found another reference to 2-hour shifts:

Clock shifts are usually scheduled near a weekend midnight to lessen
disruption to weekday schedules. A one-hour shift is customary, but
Australia's Lord Howe Island uses a half-hour shift.[25] Twenty-minute
and two-hour shifts have been used in the past.

A difference of two hours from standard time does not necessarily imply
a two-hour clock jump. During most of WWII, the UK was in Summer two
hours ahead of GMT; but was one hour ahead in Winter. The change
between normal (GMT+1, GMT) and that was achieved by omitting a step,
the reverse not by doubling but by duplicating one. In 1947, there were
two separate one-hour steps in each direction.

Germany then Britain had DST during WW I.

True, except that neither called it DST ; the European term is Summer
Time or linguistic equivalent ; but the first British use of advanced
time, on 1915-09-26, preceded the German one about six months later.

according to

http://www.timeanddate.com/news/time/uk-debates-to-extend-dst.html
However, there were periods, especially during World War II, when the
start and end dates were altered or more substantial clock shifts were
made.

More substantial changes were NOT made in the UK. Instead, two changes
were omitted. Evidently, you have not read, or believed, or remembered,
my page uksumtim.htm.

Before 1970, UK rules changed about once a decade. In fact, the UK has
never fixed perpetual rules in the US manner; arrangements for a rather
few years in advance have been settled formally by the Sovereign in
Council, in the light of custom and advice. Our current rules are
actually settled by the EU, I believe in a vaguely similar fashion.
(This refers to Britain, not the USA. This is probably what I recall
from the alleged blue book, after all Britain and the USA are both
foreign countries,separated only by language.)

according to
http://www.timeanddate.com/news/time/france-spain-summer-time.html
France and Spain have peculiar form DST informally called Double DST.

Not if you read the article carefully enough. The situation is that,
for Standard Time GMT+1, substantial parts of France and Spain are
incorrectly positioned.

All of the EU and the adjacent European countries change clocks by the
same amount at the same instant (+-<=0.9s); the rest of the fUSSR
changes by the same amount on the same date at a fixed local time.
 
A

Arne Vajhøj

Lew said:
The Spanish Civil War, albeit unofficially.

I don't think the US were much involved in that.

The democracies was still working with diplomacy at
the time. Hitler, Mussolini and Stalin tested their
airplanes and tanks.

Arne
 
L

Lew

Arne said:
I don't think the US were much involved in that.

The democracies was still working with diplomacy at
the time. Hitler, Mussolini and Stalin tested their
airplanes and tanks.

The U.S. was not officially involved, as I said, but many major U.S
corporations were, and many Americans wound up fighting in that war. There
was a strong covert U.S. involvement.
 
R

RedGrittyBrick

Martin said:
However, I digress. I remember, back in the late '90s, reading the Debian
date and time database for the UK. That's the database that records when
calendars and time standards changed. Back then it still a huge, heavily
annotated text file whose comments often included the text of e-mail
discussions about historic calendar changes and esoterica suck as whether
even regional time of day had a valid meaning before the railways came.
It was a fascinating read and I wish I'd kept a copy because its
apparently vanished in a puff of tachyons. I've looked for it a few times
but without success.

I guess you've looked at http://www.twinsun.com/tz/tz-link.htm which,
sadly, has some stale links. There are several large heavily annotated
files in ftp://elsie.nci.nih.gov/pub/tzdata2009n.tar.gz

I haven't looked for a repository of old Debian sources but I'm
surprised it isn't possible to obtain almost any version of any
mainstream Linux distro ever released. Sad if true.
 
M

Martin Gregorie

Thanks for the link. That is a really useful reference.

The Best of Dates, The Worst of Dates:
http://exit109.com/~ghealton/y2k/yrexamples.html

is linked from it and covers ancient historic stuff I'd originally
mentioned as not being able to find: standard times and DST are easy to
track down since they only go back to the mid 1800s.

When I last looked, some time ago, this didn't come up in the search list.

The Best of Dates,.... describes the Julian Day and Modified Julian Day
calendar, an astronomical date system, used by astronomers,
geophysicists, chronologers, and others who needed to have an unambiguous
dating system based on continuing day counts. It is known as Modified
Julian Day, which is based on an unbroken day number sequence, with day
zero being Wednesday, 1 JAN -4712 (4713 BC). There should be more detail,
but its a broken link. Here's a reference to a Julian Day page that works:

http://tycho.usno.navy.mil/mjd.html
 

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