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History log of /src/lib/libc/time/Theory
RevisionDateAuthorComments
 1.23  11-Mar-2017  christos merge 2017a
 1.22  20-Oct-2016  christos branches: 1.22.2;
welcome to 2016h
 1.21  07-Oct-2016  christos merge tzcode2016g
 1.20  16-Sep-2016  christos welcome to tzcond-2016f
 1.19  15-Mar-2016  christos branches: 1.19.2;
Sync with 2016b
 1.18  13-Aug-2015  christos merge 2015f
 1.17  24-Mar-2015  christos merge 2015b
 1.16  07-Oct-2014  christos Sync with tzcode2014h
 1.15  15-Aug-2014  christos merge tzcode2014f via patch
 1.14  20-Sep-2013  christos branches: 1.14.4;
Welcome to tzcode 2013e:

Changes affecting API

The 'zic' command now outputs a dummy transition when far-future
data can't be summarized using a TZ string, and uses a 402-year
window rather than a 400-year window. For the current data, this
affects only the Asia/Tehran file. It does not affect any of the
time stamps that this file represents, so zdump outputs the same
information as before. (Thanks to Andrew Main (Zefram).)

The 'date' command has a new '-r' option, which lets you specify
the integer time to display, a la FreeBSD.

The 'tzselect' command has two new options '-c' and '-n', which lets you
select a zone based on latitude and longitude.

The 'zic' command's '-v' option now warns about constructs that
require the new version-3 binary file format. (Thanks to Arthur
David Olson for the suggestion.)

Support for floating-point time_t has been removed.
It was always dicey, and POSIX no longer requires it.
(Thanks to Eric Blake for suggesting to the POSIX committee to
remove it, and thanks to Alan Barrett, Clive D.W. Feather, Andy
Heninger, Arthur David Olson, and Alois Treindl, for reporting
bugs and elucidating some of the corners of the old floating-point
implementation.)

The signatures of 'offtime', 'timeoff', and 'gtime' have been
changed back to the old practice of using 'long' to represent UT
offsets. This had been inadvertently and mistakenly changed to
'int_fast32_t'. (Thanks to Christos Zoulos.)

The code avoids undefined behavior on integer overflow in some
more places, including gmtime, localtime, mktime and zdump.

Changes affecting the zdump utility

zdump now outputs "UT" when referring to Universal Time, not "UTC".
"UTC" does not make sense for time stamps that predate the introduction
of UTC, whereas "UT", a more-generic term, does. (Thanks to Steve Allen
for clarifying UT vs UTC.)

Data changes affecting behavior of tzselect and similar programs

Country code BQ is now called the more-common name "Caribbean Netherlands"
rather than the more-official "Bonaire, St Eustatius & Saba".

Remove from zone.tab the names America/Montreal, America/Shiprock,
and Antarctica/South_Pole, as they are equivalent to existing
same-country-code zones for post-1970 time stamps. The data for
these names are unchanged, so the names continue to work as before.

Changes affecting code internals

zic -c now runs way faster on 64-bit hosts when given large numbers.

zic now uses vfprintf to avoid allocating and freeing some memory.

tzselect now computes the list of continents from the data,
rather than have it hard-coded.

Minor changes pacify GCC 4.7.3 and GCC 4.8.1.

Changes affecting the build procedure

The 'leapseconds' file is now generated automatically from a
new file 'leap-seconds.list', which is a copy of
<ftp://time.nist.gov/pub/leap-seconds.list>.
A new source file 'leapseconds.awk' implements this.
The goal is simplification of the future maintenance of 'leapseconds'.

When building the 'posix' or 'right' subdirectories, if the
subdirectory would be a copy of the default subdirectory, it is
now made a symbolic link if that is supported. This saves about
2 MB of file system space.

The links America/Shiprock and Antarctica/South_Pole have been
moved to the 'backward' file. This affects only nondefault builds
that omit 'backward'.

Changes affecting documentation and commentary

Changes to the 'tzfile' man page

It now mentions that the binary file format may be extended in
future versions by appending data.

It now refers to the 'zdump' and 'zic' man pages.

Changes to the 'zic' man page

It lists conditions that elicit a warning with '-v'.

It says that the behavior is unspecified when duplicate names
are given, or if the source of one link is the target of another.

Its examples are updated to match the latest data.

The definition of white space has been clarified slightly.
(Thanks to Michael Deckers.)

Changes to the 'Theory' file

There is a new section about the accuracy of the tz database,
describing the many ways that errors can creep in, and
explaining why so many of the pre-1970 time stamps are wrong or
misleading (thanks to Steve Allen, Lester Caine, and Garrett
Wollman for discussions that contributed to this).

The 'Theory' file describes LMT better (this follows a
suggestion by Guy Harris).

It refers to the 2013 edition of POSIX rather than the 2004 edition.

It's mentioned that excluding 'backward' should not affect the
other data, and it suggests at least one zone.tab name per
inhabited country (thanks to Stephen Colebourne).

Some longstanding restrictions on names are documented, e.g.,
'America/New_York' precludes 'America/New_York/Bronx'.

It gives more reasons for the 1970 cutoff.

It now mentions which time_t variants are supported, such as
signed integer time_t. (Thanks to Paul Goyette for reporting
typos in an experimental version of this change.)

(Thanks to Philip Newton for correcting typos in these changes.)

Documentation and commentary is more careful to distinguish UT in
general from UTC in particular. (Thanks to Steve Allen.)

Add a better source for the Zurich 1894 transition.
(Thanks to Pierre-Yves Berger.)

Update shapefile citations in tz-link.htm. (Thanks to Guy Harris.)
 1.13  17-Jul-2013  christos welcome to 2013d
 1.12  28-Oct-2012  christos branches: 1.12.2;
welcome to tzcode2012h via patch.
 1.11  09-Aug-2012  christos branches: 1.11.2;
merge 2012e
 1.10  04-Sep-2011  christos branches: 1.10.2;
bring in the 2011i changes.
 1.9  31-Dec-2009  mlelstv Import tzcode2009k.
- now understands 64bit time_t and 64bit data in timezone files.
- localtime(), gmtime(), asctime() and ctime() may now fail with
a NULL result if time_t cannot be represented by struct tm.
 1.8  27-May-2004  kleink Merge tzcode2004a.
 1.7  20-Dec-2003  kleink branches: 1.7.2;
Merge tzcode2003e.
 1.6  29-Jan-2002  kleink Merge tzcode2002b.
 1.5  12-Dec-2000  kleink branches: 1.5.2;
Merge tzcode2000g.
 1.4  10-Nov-1999  kleink Merge tzcode1999h.
 1.3  22-Jan-1998  jtc branches: 1.3.6;
sync with tzcode1998a
 1.2  09-Jan-1998  perry RCS Id Police.
 1.1  10-Mar-1995  jtc branches: 1.1.1;
Initial revision
 1.1.1.10  25-Oct-2009  mlelstv import tzcode2009k
 1.1.1.9  27-May-2004  kleink Import tzcode2004a.
 1.1.1.8  19-Dec-2003  kleink Import tzcode2003e.
 1.1.1.7  29-Jan-2002  kleink Import tzcode2002b.
 1.1.1.6  12-Dec-2000  kleink Import tzcode2000g.
 1.1.1.5  10-Nov-1999  kleink Import tzcode1999h.
 1.1.1.4  22-Jan-1998  jtc import tzcode1998a
 1.1.1.3  05-Sep-1997  jtc import tzcode1997g
 1.1.1.2  08-Jan-1996  jtc import tzcode96a
 1.1.1.1  10-Mar-1995  jtc branches: 1.1.1.1.2;
Strictly speaking, these files probably don't belong in the libc sources.
On the other hand, it makes it easier to track the master tzcode sources
if we try to keep the distribution together as much as possible.

The zic and zdump commands will access the files the need with make's
.PATH facility.
 1.1.1.1.2.2  10-Mar-1995  jtc Strictly speaking, these files probably don't belong in the libc sources.
On the other hand, it makes it easier to track the master tzcode sources
if we try to keep the distribution together as much as possible.

The zic and zdump commands will access the files the need with make's
.PATH facility.
 1.1.1.1.2.1  10-Mar-1995  jtc file Theory was added on branch ivory_soap on 1995-03-10 07:08:17 +0000
 1.3.6.1  27-Dec-1999  wrstuden Pull up to last week's -current.
 1.5.2.1  08-Mar-2002  nathanw Catch up to -current.
 1.7.2.1  15-Jun-2004  he Pull up revision 1.8 (requested by kleink in ticket #407):
Update to tzcode2004a.
 1.10.2.2  22-May-2014  yamt sync with head.

for a reference, the tree before this commit was tagged
as yamt-pagecache-tag8.

this commit was splitted into small chunks to avoid
a limitation of cvs. ("Protocol error: too many arguments")
 1.10.2.1  30-Oct-2012  yamt sync with head
 1.11.2.2  20-Aug-2014  tls Rebase to HEAD as of a few days ago.
 1.11.2.1  20-Nov-2012  tls Resync to 2012-11-19 00:00:00 UTC
 1.12.2.1  23-Jul-2013  riastradh sync with HEAD
 1.14.4.1  25-Jan-2015  martin Pull up the following revisions via patch, requested by apb in ticket #453:

doc/3RDPARTY up to 1.1195
usr.sbin/zdump/Makefile up to 1.9
usr.sbin/zic/Makefile up to 1.15
lib/libc/time/Makefile up to 1.25
lib/libc/time/Makefile.inc up to 1.21
lib/libc/time/NEWS up to 1.8
lib/libc/time/README up to 1.9
lib/libc/time/Theory up to 1.16
lib/libc/time/asctime.c up to 1.20
lib/libc/time/checktab.awk up to 1.8
lib/libc/time/ctime.3 up to 1.51
lib/libc/time/getdate.c up to 1.3
lib/libc/time/localtime.c up to 1.92
lib/libc/time/private.h up to 1.38
lib/libc/time/strftime.c up to 1.33
lib/libc/time/time2posix.3 up to 1.19
lib/libc/time/tz-art.htm up to 1.8
lib/libc/time/tz-link.htm up to 1.20
lib/libc/time/tzfile.5 up to 1.22
lib/libc/time/tzfile.h up to 1.16
lib/libc/time/tzselect.8 up to 1.6
lib/libc/time/tzselect.ksh up to 1.12
lib/libc/time/tzset.3 up to 1.31
lib/libc/time/zdump.8 up to 1.14
lib/libc/time/zdump.c up to 1.40
lib/libc/time/zic.8 up to 1.24
lib/libc/time/zic.c up to 1.52

Update tzcode from 2014e to 2014j.
 1.19.2.2  20-Mar-2017  pgoyette Sync with HEAD
 1.19.2.1  04-Nov-2016  pgoyette Sync with HEAD
 1.22.2.1  21-Apr-2017  bouyer Sync with HEAD

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