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tzfile.5: Sync from tzdb upstream 

Make tzfile.5 a copy of the upstream tzdb version, except that
the tzdb version's first line is replaced by man-pages
boilerplate.

This has the following effect:

Do some minor spec fixes, notably about time type 0
and empty TZ strings.  Omit some changes that were made on the
man-pages side, notably by changing some "timezone"s back to the
preferred-upstream "time zone" when talking about traditional
time zones as opposed to POSIX timezone settings.
Also, fix some formatting glitches.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Paul Eggert 2018-06-27 12:52:35 -07:00 committed by Michael Kerrisk
parent 53666f6c30
commit a312fa038d
1 changed files with 28 additions and 21 deletions
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49
man5/tzfile.5
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@ -3,8 +3,6 @@
.\" 1996-06-05 by Arthur David Olson <arthur_david_olson@nih.gov>.
.\" %%%LICENSE_END
.\"
.\" @(#)tzfile.5 7.11
.\"
.TH TZFILE 5 2017-08-04 "" "Linux Programmer's Manual"
.SH NAME
tzfile \- timezone information
@ -59,12 +57,12 @@ The number of local time types for which data entries are stored
in the file (must not be zero).
.TP
.I tzh_charcnt
The number of bytes of timezone abbreviation strings
The number of bytes of time zone abbreviation strings
stored in the file.
.RE
.PP
The above header is followed by the following fields, whose lengths
vary depend on the contents of the header:
depend on the contents of the header:
.IP * 2
.I tzh_timecnt
four-byte signed integer values sorted in ascending order.
@ -75,25 +73,29 @@ at which the rules for computing local time change.
.IP *
.I tzh_timecnt
one-byte unsigned integer values;
each one tells which of the different types of local time types
each one but the last tells which of the different types of local time types
described in the file is associated with the time period
starting with the same-indexed transition time.
starting with the same-indexed transition time
and continuing up to but not including the next transition time.
(The last time type is present only for consistency checking with the
POSIX-style TZ string described below.)
These values serve as indices into the next field.
.IP *
.I tzh_typecnt
.I ttinfo
entries, each defined as follows:
.PP
.in +4n
.EX
.in +.5i
.sp
.nf
.ta .5i +\w'unsigned char\0\0'u
struct ttinfo {
int32_t tt_gmtoff;
unsigned char tt_isdst;
unsigned char tt_abbrind;
int32_t tt_gmtoff;
unsigned char tt_isdst;
unsigned char tt_abbrind;
};
.EE
.in
.PP
.in -.5i
.fi
.sp
Each structure is written as a four-byte signed integer value for
.IR tt_gmtoff ,
in a standard byte order, followed by a one-byte value for
@ -110,7 +112,7 @@ should be set by
.BR localtime (3)
and
.I tt_abbrind
serves as an index into the array of timezone abbreviation bytes
serves as an index into the array of time zone abbreviation bytes
that follow the
.I ttinfo
structure(s) in the file.
@ -165,21 +167,26 @@ eight bytes are used for each transition time or leap second time.
After the second header and data comes a newline-enclosed,
POSIX-TZ-environment-variable-style string for use in handling instants
after the last transition time stored in the file
(with nothing between the newlines if there is no POSIX representation for
such instants).
The POSIX-style string must agree with the local time type after
both data's last transition times; for example, given the string
or for all instants if the file has no transitions.
The POSIX-style TZ string is empty (i.e., nothing between the newlines)
if there is no POSIX representation for such instants.
If nonempty, the POSIX-style TZ string must agree with the local time
type after the last transition time if present in the eight-byte data;
for example, given the string
.q "WET0WEST,M3.5.0,M10.5.0/3"
then if a last transition time is in July, the transition's local time
type must specify a daylight-saving time abbreviated
.q "WEST"
that is one hour east of UT.
Also, if there is at least one transition, time type 0 is associated
with the time period from the indefinite past up to but not including
the earliest transition time.
.SS Version 3 format
For version-3-format timezone files, the POSIX-TZ-style string may
use two minor extensions to the POSIX TZ format, as described in
.BR newtzset (3).
First, the hours part of its transition times may be signed and range from
\-167 through 167 instead of the POSIX-required unsigned values
\*-167 through 167 instead of the POSIX-required unsigned values
from 0 through 24.
Second, DST is in effect all year if it starts
January 1 at 00:00 and ends December 31 at 24:00 plus the difference