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From: mi...@crash.cts.com (Mike Lemons)
Subject: When Does Daylight Savings Time Change?
Organization: Multicellular, carbon-based lifeform
Date: Fri, 2 Sep 1994 21:16:56 GMT
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I'm writing a routine to do an automatic daylight savings time change.
Unfortunately, I don't understand the rules very well. On the last
Saturday in October, you set the clock back one hour. On the first
Saturday in April, you set the clock forward one hour. The problem with
that description is that the change actually occurs at 3am or 2am on
the following Sunday. What happens when Saturday and Sunday are in
different months?
For example, would you set the clock back at 3am on the 25th or Sep 1st?
10/31/98 is the last Saturday in October:
October 1998
S M Tu W Th F S
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
Would you set the clock forward at 2am on the 1st or 8th?
4/01/01 is the first Sunday in April:
April 2001
S M Tu W Th F S
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30
------------------------------------------------------------------------------
mi...@crash.cts.com | Don't confuse making | "Why should we bother to do
Mike Lemons | things illegal with | anything if it's all just
| leadership and | going to fall in a black hole
| governing a nation. | some day?" - an ex girlfriend
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From: w...@netcom.com (William J. Evans)
Subject: Re: When Does Daylight Savings Time Change?
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Mike Lemons (mi...@crash.cts.com) wrote:
: I'm writing a routine to do an automatic daylight savings time change.
: Unfortunately, I don't understand the rules very well. On the last
: Saturday in October, you set the clock back one hour. On the first
: Saturday in April, you set the clock forward one hour. The problem with
: that description is that the change actually occurs at 3am or 2am on
: the following Sunday. What happens when Saturday and Sunday are in
: different months?
Forget the Saturday stuff.
On the first Sunday in April, in the wee hours of the morning, when
it's 2:00am, set the clock to 3:00am. On the last Sunday in October,
when it's 2:00am, set the clock to 1:00am (not 3:00 to 2:00).
In the United States, only Arizona and Indiana do not use Daylight
Savings Time.
-- Bill Evans
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From: dan...@cernapo.cern.ch (Dan Pop)
Subject: Re: When Does Daylight Savings Time Change?
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In <wjeCvM172....@netcom.com> w...@netcom.com (William J. Evans) writes:
>Mike Lemons (mi...@crash.cts.com) wrote:
>: I'm writing a routine to do an automatic daylight savings time change.
>: Unfortunately, I don't understand the rules very well. On the last
>: Saturday in October, you set the clock back one hour. On the first
>: Saturday in April, you set the clock forward one hour. The problem with
>: that description is that the change actually occurs at 3am or 2am on
>: the following Sunday. What happens when Saturday and Sunday are in
>: different months?
>
>Forget the Saturday stuff.
>
>On the first Sunday in April, in the wee hours of the morning, when
>it's 2:00am, set the clock to 3:00am. On the last Sunday in October,
>when it's 2:00am, set the clock to 1:00am (not 3:00 to 2:00).
>
>In the United States, only Arizona and Indiana do not use Daylight
>Savings Time.
And in Europe it's the last Sunday in March and the last Sunday in
September, at midnight (0:00am --> 1:00am and 1:00am --> 0:00am).
Dan
--
Dan Pop
CERN, CN Division
Email: dan...@cernapo.cern.ch
Mail: CERN - PPE, Bat. 31 R-004, CH-1211 Geneve 23, Switzerland
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From: w...@netcom.com (William J. Evans)
Subject: Re: When Does Daylight Savings Time Change?
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Date: Mon, 5 Sep 1994 14:47:55 GMT
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Dan Pop (dan...@cernapo.cern.ch) wrote:
: And in Europe it's the last Sunday in March and the last Sunday in
: September, at midnight (0:00am --> 1:00am and 1:00am --> 0:00am).
Are there any countries in Europe or the Middle East which either do
not have Daylight Savings Time (rather like the countries of Arizona
and Indiana) or which use a different convention?
-- Bill Evans
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From: lo...@ismennt.is (Logi Ragnarsson)
Newsgroups: comp.lang.c
Subject: Re: When Does Daylight Savings Time Change?
Date: 5 Sep 1994 22:42:35 -0000
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w...@netcom.com (William J. Evans) writes:
>Dan Pop (dan...@cernapo.cern.ch) wrote:
>: And in Europe it's the last Sunday in March and the last Sunday in
>: September, at midnight (0:00am --> 1:00am and 1:00am --> 0:00am).
>Are there any countries in Europe or the Middle East which either do
>not have Daylight Savings Time (rather like the countries of Arizona
>and Indiana) or which use a different convention?
Well, there is no daylight savings time in Iceland, and I would assume
some other places would not bother about it. There is little point this
far north.
Logi - lo...@ismennt.is
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From: ken...@cs.utwente.nl (Arjan Kenter)
Subject: Re: When Does Daylight Savings Time Change?
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<CvMAsJ.94r@news.cern.ch> <wjeCvnvrw.IBF@netcom.com> <34g6sr$2nn@rvik.ismennt.is>
Date: Tue, 6 Sep 1994 08:31:02 GMT
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In article <34g6sr$...@rvik.ismennt.is>, lo...@ismennt.is (Logi Ragnarsson)
writes:
> w...@netcom.com (William J. Evans) writes:
>
> >Dan Pop (dan...@cernapo.cern.ch) wrote:
> >: And in Europe it's the last Sunday in March and the last Sunday in
> >: September, at midnight (0:00am --> 1:00am and 1:00am --> 0:00am).
>
> >Are there any countries in Europe or the Middle East which either do
> >not have Daylight Savings Time (rather like the countries of Arizona
> >and Indiana) or which use a different convention?
>
> Well, there is no daylight savings time in Iceland, and I would assume
> some other places would not bother about it. There is little point this
> far north.
Also in Israel (maybe the rest of the Middle East too? Don't know) they have
another day. I remember the day I started my internship at the Technion in
Haifa, Israel, DST ended. Unfortunately, nobody had told me about it, so I
wondered why come it was so quiet on the university campus and why my
supervisor was late. He showed up an hour late! And when I asked him, he
replied like "Why? It's nine o'clock," when it was ten at my wristwatch...
This was the last Sunday of August '90 if I remember correctly (Sunday is
a working day in Israel).
--
^^
ir. H.J.H.N. Kenter oo ) ken...@cs.utwente.nl
University of Twente =x= \ tel. +31 53 893747
Tele-Informatics & Open Systems | \ tfx. +31 53 333815
P.O. Box 217 7500 AE Enschede /|__ \
The Netherlands (____)_/
As long as the answer is right, who cares if the question is wrong?
I never saw this cookie so I may not agree with it!
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From: to...@elf.bsdi.com (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: When Does Daylight Savings Time Change?
Date: 6 Sep 1994 07:37:26 -0700
Organization: Berkeley Software Design, Inc.
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In article <Cvp8zr....@cs.utwente.nl> Arjan Kenter <ken...@cs.utwente.nl>
writes:
>Also in Israel ... they have another day.
The rules for Israel, like those for just about everywhere on the
earth, are available in the Arthur Olson time zone package (available
as part of all current BSDs, including the 4.4-lite, FreeBSD, and
NetBSD). Here is an excerpt from the `asia' table.
# Israel
# From U. S. Naval Observatory (January 19, 1989):
# ISRAEL 2 H AHEAD OF UTC
# ISRAEL 3 H AHEAD OF UTC APR 10 - SEP 3
# From Ephraim Silverberg (April 18, 1989):
# Prior to 1989, the rules concerning Daylight Savings Time changed every
# year; as information, regarding exact times and dates during this period,
# is not readily available at the present time, the rules commence starting
# with the year 1989.
# From 1989 onwards the rules are as follows:
#
# 1. Daylight Savings Time commences midnight of the first Saturday night
# following the seven-day festival of Pesach (Passover). The transition
# is from midnight Israel Standard Time to 1 a.m. Israel Daylight Savings
# time. As the Pesach festival is dependent on the Lunar calendar (the
# first day is always on the 15th day of the month of Nisan), the rule
# changes every year on the Gregorian calendar.
#
# 2. Standard Time is reinstated on the Saturday night whereupon Jews
# following the Ashkenazi (European) rite begin to recite the Selichot
# (forgiveness) prayers prior to the Jewish Lunar New Year. The transition
# is from midnight Israel Daylight Savings time to 11 p.m. Israel Standard
# Time. The law (according to the Ashkenazi custom) concerning the
# commencement of the Selichot prayers is described in chapter 128, section
# 5 of the "Code of Jewish Law," by Rabbi Shlomo Ganzfried (translated by
# Hyman E. Goldin):
#
# Beginning with the Sunday [**] before Rosh Hashanah [***],
# we rise early for the service of Selichot (supplications for
# forgiveness). If Rosh Hashanah occurs on Monday or Tuesday, we
# begin saying the Selichot from the Sunday of the preceding week.
#
# This, too, varies from year to year on the Gregorian calendar and, thus,
# two explicit timezone rules are required for each Gregorian year.
#
# [**] actually Saturday night as the Jewish day commences at nightfall.
# [***] the Jewish Lunar New Year.
# Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
Rule Zion 1989 only - Apr 30 0:00 1:00 D
Rule Zion 1989 only - Sep 24 0:00 0:00 S
Rule Zion 1990 only - Apr 22 0:00 1:00 D
Rule Zion 1990 only - Sep 16 0:00 0:00 S
Rule Zion 1991 only - Apr 7 0:00 1:00 D
Rule Zion 1991 only - Sep 1 0:00 0:00 S
Rule Zion 1992 only - Apr 26 0:00 1:00 D
Rule Zion 1992 only - Sep 20 0:00 0:00 S
Rule Zion 1993 only - Apr 18 0:00 1:00 D
Rule Zion 1993 only - Sep 12 0:00 0:00 S
Rule Zion 1994 only - Apr 3 0:00 1:00 D
Rule Zion 1994 only - Aug 28 0:00 0:00 S
Rule Zion 1995 only - Apr 23 0:00 1:00 D
Rule Zion 1995 only - Sep 17 0:00 0:00 S
Rule Zion 1996 only - Apr 14 0:00 1:00 D
Rule Zion 1996 only - Sep 8 0:00 0:00 S
Rule Zion 1997 only - May 4 0:00 1:00 D
Rule Zion 1997 only - Sep 28 0:00 0:00 S
Rule Zion 1998 only - Apr 19 0:00 1:00 D
Rule Zion 1998 only - Sep 13 0:00 0:00 S
Rule Zion 1999 only - Apr 11 0:00 1:00 D
Rule Zion 1999 only - Sep 5 0:00 0:00 S
Rule Zion 2000 only - Apr 30 0:00 1:00 D
Rule Zion 2000 only - Sep 24 0:00 0:00 S
Rule Zion 2001 only - Apr 15 0:00 1:00 D
Rule Zion 2001 only - Sep 9 0:00 0:00 S
Rule Zion 2002 only - Apr 7 0:00 1:00 D
Rule Zion 2002 only - Sep 1 0:00 0:00 S
Rule Zion 2003 only - Apr 27 0:00 1:00 D
Rule Zion 2003 only - Sep 21 0:00 0:00 S
Rule Zion 2004 only - Apr 18 0:00 1:00 D
Rule Zion 2004 only - Sep 12 0:00 0:00 S
Rule Zion 2005 only - May 1 0:00 1:00 D
Rule Zion 2005 only - Sep 25 0:00 0:00 S
Rule Zion 2006 only - Apr 23 0:00 1:00 D
Rule Zion 2006 only - Sep 17 0:00 0:00 S
Rule Zion 2007 only - Apr 15 0:00 1:00 D
Rule Zion 2007 only - Sep 9 0:00 0:00 S
Rule Zion 2008 only - Apr 27 0:00 1:00 D
Rule Zion 2008 only - Sep 21 0:00 0:00 S
Rule Zion 2009 only - Apr 19 0:00 1:00 D
Rule Zion 2009 only - Sep 13 0:00 0:00 S
# Zone NAME GMTOFF RULES/SAVE FORMAT [UNTIL]
Zone Israel 2:00 Zion I%sT
# The following is a chart of the day of the week and Gregorian date of
# the first day of Pesach and the first day of Rosh Hashanah for the years
# 1989 through 2009 inclusive.
#
# First Day of Passover
# ---------------------
# Gregorian Year Day of Week Month Day
# -------------- ----------- ----- ---
# 1989 Thursday April 20
# 1990 Tuesday April 10
# 1991 Saturday March 30
# 1992 Saturday April 18
# 1993 Tuesday April 6
# 1994 Sunday March 27
# 1995 Saturday April 15
# 1996 Thursday April 4
# 1997 Tuesday April 22
# 1998 Saturday April 11
# 1999 Thursday April 1
# 2000 Thursday April 20
# 2001 Sunday April 8
# 2002 Thursday March 28
# 2003 Thursday April 17
# 2004 Tuesday April 6
# 2005 Sunday April 24
# 2006 Thursday April 13
# 2007 Tuesday April 3
# 2008 Sunday April 20
# 2009 Thursday April 9
#
# First Day of Rosh Hashanah
# --------------------------
# Gregorian Year Day of Week Month Day
# -------------- ----------- ----- ---
# 1989 Saturday September 30
# 1990 Thursday September 20
# 1991 Monday September 9
# 1992 Monday September 28
# 1993 Thursday September 16
# 1994 Tuesday September 6
# 1995 Monday September 25
# 1996 Saturday September 14
# 1997 Thursday October 2
# 1998 Monday September 21
# 1999 Saturday September 11
# 2000 Saturday September 30
# 2001 Tuesday September 18
# 2002 Saturday September 7
# 2003 Saturday September 27
# 2004 Thursday September 16
# 2005 Tuesday October 4
# 2006 Saturday September 23
# 2007 Thursday September 13
# 2008 Tuesday September 30
# 2009 Saturday September 19
--
In-Real-Life: Chris Torek, Berkeley Software Design Inc
Berkeley, CA Domain: to...@bsdi.com +1 510 549 1145
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From: egg...@twinsun.com (Paul Eggert)
Subject: Re: When Does Daylight Savings Time Change?
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<34g6sr$2nn@rvik.ismennt.is> <Cvp8zr.E9t@cs.utwente.nl> <34hur6$qvb@elf.bsdi.com>
Date: Fri, 16 Sep 1994 17:27:19 GMT
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to...@elf.bsdi.com (Chris Torek) writes:
> The rules for Israel, like those for just about everywhere on the
> earth, are available in the Arthur Olson time zone package (available
> as part of all current BSDs, including the 4.4-lite, FreeBSD, and
> NetBSD). Here is an excerpt from the `asia' table.
Alas, that April 1989 excerpt is woefully out of date -- Israel changes
time zone rules more often than it changes governments, and by
September 1989 they had already changed the rules again.
Whatever BSD you got it from should update its tables
from the latest version in elsie.nci.nih.gov in pub/tz*.
Time zone rules are intensely political in Israel -- e.g. I've heard
that in the occupied territories the resistance used time zone rules
that differed from the government's, and I don't know what the new
Palestinian government is doing about this. It would be nice to send
future corrections to the email address given in the tables.
I strongly second the suggestion of using mktime() and the tz package
to answer questions like ``when does daylight savings time change?''.
Why reinvent the wheel? The tz package even comes with a program
`zdump' that answers this very question, and its source code is
portable and is in the public domain.