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Revision 1.1, Tue Oct 24 17:38:17 2017 UTC (4 years ago) by christos
Branch: MAIN
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Welcome to 2017c:

    zic and the reference runtime now reject multiple leap seconds
    within 28 days of each other, or leap seconds before the Epoch.
    As a result, support for double leap seconds, which was
    obsolescent and undocumented, has been removed.  Double leap
    seconds were an error in the C89 standard; they have never existed
    in civil timekeeping.  (Thanks to Robert Elz and Bradley White for
    noticing glitches in the code that uncovered this problem.)

    zic now warns about use of the obsolescent and undocumented -y
    option, and about use of the obsolescent TYPE field of Rule lines.

    zic now allows unambiguous abbreviations like "Sa" and "Su" for
    weekdays; formerly it rejected them due to a bug.  Conversely, zic
    no longer considers non-prefixes to be abbreviations; for example,
    it no longer accepts "lF" as an abbreviation for "lastFriday".
    Also, zic warns about the undocumented usage with a "last-"
    prefix, e.g., "last-Fri".

    Similarly, zic now accepts the unambiguous abbreviation "L" for
    "Link" in ordinary context and for "Leap" in leap-second context.
    Conversely, zic no longer accepts non-prefixes such as "La" as
    abbreviations for words like "Leap".

    zic no longer accepts leap second lines in ordinary input, or
    ordinary lines in leap second input.  Formerly, zic sometimes
    warned about this undocumented usage and handled it incorrectly.

    The new macro HAVE_TZNAME governs whether the tzname external
    variable is exported, instead of USG_COMPAT.  USG_COMPAT now
    governs only the external variables "timezone" and "daylight".
    This change is needed because the three variables are not in the
    same category: although POSIX requires tzname, it specifies the
    other two variables as optional.  Also, USG_COMPAT is now 1 or 0:
    if not defined, the code attempts to guess it from other macros.

    localtime.c and difftime.c no longer require stdio.h, and .c files
    other than zic.c no longer require sys/wait.h.

    zdump.c no longer assumes snprintf.  (Reported by Jonathan Leffler.)

    Calculation of time_t extrema works around a bug in GCC 4.8.4
    (Reported by Stan Shebs and Joseph Myers.)

    zic.c no longer mistranslates formats of line numbers in non-English
    locales.  (Problem reported by Benno Schulenberg.)

    Several minor changes have been made to the code to make it a
    bit easier to port to MS-Windows and Solaris.  (Thanks to Kees
    Dekker for reporting the problems.)

  Changes to documentation and commentary

    The two new files 'theory.html' and 'calendars' contain the
    contents of the removed file 'Theory'.  The goal is to document
    tzdb theory more accessibly.

    The zic man page now documents abbreviation rules.

    tz-link.htm now covers how to apply tzdata changes to clients.
    (Thanks to Jorge Fábregas for the AIX link.)  It also mentions MySQL.

    The leap-seconds.list URL has been updated to something that is
    more reliable for tzdb.  (Thanks to Tim Parenti and Brian Inglis.)

----- Calendrical issues -----

As mentioned in Theory.html, although calendrical issues are out of
scope for tzdb, they indicate the sort of problems that we would run
into if we extended tzdb further into the past.  The following
information and sources go beyond Theory.html's brief discussion.
They sometimes disagree.


Gregorian calendar adopted 1582-12-20.
French Revolutionary calendar used 1793-11-24 through 1805-12-31,
and (in Paris only) 1871-05-06 through 1871-05-23.


From Chris Carrier (1996-12-02):
On 1929-10-01 the Soviet Union instituted an "Eternal Calendar"
with 30-day months plus 5 holidays, with a 5-day week.
On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the
Gregorian calendar while retaining the 6-day week; on 1940-06-27 it
reverted to the 7-day week.  With the 6-day week the usual days
off were the 6th, 12th, 18th, 24th and 30th of the month.
(Source: Evitiar Zerubavel, _The Seven Day Circle_)

Mark Brader reported a similar story in "The Book of Calendars", edited
by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377.  But:

From: Petteri Sulonen (via Usenet)
Date: 14 Jan 1999 00:00:00 GMT

If your source is correct, how come documents between 1929 and 1940 were
still dated using the conventional, Gregorian calendar?

I can post a scan of a document dated December 1, 1934, signed by
Yenukidze, the secretary, on behalf of Kalinin, the President of the
Executive Committee of the Supreme Soviet, if you like.

Sweden (and Finland)

From: Mark Brader
Subject: Re: Gregorian reform - a part of locale?
Date: 1996-07-06

In 1700, Denmark made the transition from Julian to Gregorian.  Sweden
decided to *start* a transition in 1700 as well, but rather than have one of
those unsightly calendar gaps :-), they simply decreed that the next leap
year after 1696 would be in 1744 - putting the whole country on a calendar
different from both Julian and Gregorian for a period of 40 years.

However, in 1704 something went wrong and the plan was not carried through;
they did, after all, have a leap year that year.  And one in 1708.  In 1712
they gave it up and went back to Julian, putting 30 days in February that

Then in 1753, Sweden made the transition to Gregorian in the usual manner,
getting there only 13 years behind the original schedule.

(A previous posting of this story was challenged, and Swedish readers
produced the following references to support it: "Tideräkning och historia"
by Natanael Beckman (1924) and "Tid, en bok om tideräkning och
kalenderväsen" by Lars-Olof Lodén (1968).

Grotefend's data

From: "Michael Palmer" [with one obvious typo fixed]
Subject: Re: Gregorian Calendar (was Re: Another FHC related question
Newsgroups: soc.genealogy.german
Date: Tue, 9 Feb 1999 02:32:48 -800

The following is a(n incomplete) listing, arranged chronologically, of
European states, with the date they converted from the Julian to the
Gregorian calendar:

04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman
                 Catholics and Danzig only)
09/20 Dec 1582 - France, Lorraine

21 Dec 1582/
   01 Jan 1583 - Holland, Brabant, Flanders, Hennegau
10/21 Feb 1583 - bishopric of Liege (Lüttich)
13/24 Feb 1583 - bishopric of Augsburg
04/15 Oct 1583 - electorate of Trier
05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg,
                 Salzburg, Brixen
13/24 Oct 1583 - Austrian Oberelsa and Breisgau
20/31 Oct 1583 - bishopric of Basel
02/13 Nov 1583 - duchy of Jülich-Berg
02/13 Nov 1583 - electorate and city of Köln
04/15 Nov 1583 - bishopric of Würzburg
11/22 Nov 1583 - electorate of Mainz
16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden
17/28 Nov 1583 - bishopric of Münster and duchy of Cleve
14/25 Dec 1583 - Steiermark

06/17 Jan 1584 - Austria and Bohemia
11/22 Jan 1584 - Lucerne, Uri, Schwyz, Zug, Freiburg, Solothurn
12/23 Jan 1584 - Silesia and the Lausitz
22 Jan/
   02 Feb 1584 - Hungary (legally on 21 Oct 1587)
      Jun 1584 - Unterwalden
01/12 Jul 1584 - duchy of Westfalen

16/27 Jun 1585 - bishopric of Paderborn

14/25 Dec 1590 - Transylvania

22 Aug/
   02 Sep 1612 - duchy of Prussia

13/24 Dec 1614 - Pfalz-Neuburg

          1617 - duchy of Kurland (reverted to the Julian calendar in

          1624 - bishopric of Osnabrück

          1630 - bishopric of Minden

15/26 Mar 1631 - bishopric of Hildesheim

          1655 - Kanton Wallis

05/16 Feb 1682 - city of Strassburg

18 Feb/
   01 Mar 1700 - Protestant Germany (including Swedish possessions in
                 Germany), Denmark, Norway
30 Jun/
   12 Jul 1700 - Gelderland, Zutphen
10 Nov/
   12 Dec 1700 - Utrecht, Overijssel

31 Dec 1700/
   12 Jan 1701 - Friesland, Groningen, Zürich, Bern, Basel, Geneva,
                 Turgau, and Schaffhausen

          1724 - Glarus, Appenzell, and the city of St. Gallen

01 Jan 1750    - Pisa and Florence

02/14 Sep 1752 - Great Britain

17 Feb/
   01 Mar 1753 - Sweden

1760-1812      - Graubünden

The Russian empire (including Finland and the Baltic states) did not
convert to the Gregorian calendar until the Soviet revolution of 1917.

Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen
Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend
(Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28.


This file is in the public domain, so clarified as of 2009-05-17 by
Arthur David Olson.

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