Import tzcode 2022cvendor/tzcode/tzcode2022c

1 files changed, 130 insertions, 29 deletions

diff --git a/zdump.8.txt b/zdump.8.txt
index 78c647f7636b..65b6a287f3f8 100644
--- a/zdump.8.txt
+++ b/zdump.8.txt
@@ -1,43 +1,144 @@
-NAME
+ZDUMP(8)                    System Manager's Manual                   ZDUMP(8)
 
-     zdump - time zone dumper
+NAME
+       zdump - timezone dumper
 
 SYNOPSIS
-     zdump [ --version ] [ -v ] [ -c [loyear,]hiyear ] [ zonename
-     ... ]
+       zdump [ option ... ] [ timezone ... ]
 
 DESCRIPTION
-     Zdump prints the current time in each zonename named on the
-     command line.
+       The zdump program prints the current time in each timezone named on the
+       command line.
+
+OPTIONS
+       --version
+              Output version information and exit.
+
+       --help Output short usage message and exit.
+
+       -i     Output a description of time intervals.  For each timezone on
+              the command line, output an interval-format description of the
+              timezone.  See "INTERVAL FORMAT" below.
+
+       -v     Output a verbose description of time intervals.  For each
+              timezone on the command line, print the times at the two extreme
+              time values, the times (if present) at and just beyond the
+              boundaries of years that localtime(3) and gmtime(3) can
+              represent, and the times both one second before and exactly at
+              each detected time discontinuity.  Each line is followed by
+              isdst=D where D is positive, zero, or negative depending on
+              whether the given time is daylight saving time, standard time,
+              or an unknown time type, respectively.  Each line is also
+              followed by gmtoff=N if the given local time is known to be N
+              seconds east of Greenwich.
+
+       -V     Like -v, except omit output concerning extreme time and year
+              values.  This generates output that is easier to compare to that
+              of implementations with different time representations.
+
+       -c [loyear,]hiyear
+              Cut off interval output at the given year(s).  Cutoff times are
+              computed using the proleptic Gregorian calendar with year 0 and
+              with Universal Time (UT) ignoring leap seconds.  Cutoffs are at
+              the start of each year, where the lower-bound timestamp is
+              inclusive and the upper is exclusive; for example, -c 1970,2070
+              selects transitions on or after 1970-01-01 00:00:00 UTC and
+              before 2070-01-01 00:00:00 UTC.  The default cutoff is
+              -500,2500.
 
-     These options are available:
+       -t [lotime,]hitime
+              Cut off interval output at the given time(s), given in decimal
+              seconds since 1970-01-01 00:00:00 Coordinated Universal Time
+              (UTC).  The timezone determines whether the count includes leap
+              seconds.  As with -c, the cutoff's lower bound is inclusive and
+              its upper bound is exclusive.
 
-     --version
-          Output version information and exit.
+INTERVAL FORMAT
+       The interval format is a compact text representation that is intended
+       to be both human- and machine-readable.  It consists of an empty line,
+       then a line "TZ=string" where string is a double-quoted string giving
+       the timezone, a second line "- - interval" describing the time interval
+       before the first transition if any, and zero or more following lines
+       "date time interval", one line for each transition time and following
+       interval.  Fields are separated by single tabs.
 
-     -v   For each zonename on the command line, print the time
-          at the lowest possible time value, the time one day
-          after the lowest possible time value, the times both
-          one second before and exactly at each detected time
-          discontinuity, the time at one day less than the
-          highest possible time value, and the time at the
-          highest possible time value, Each line ends with
-          isdst=1 if the given time is Daylight Saving Time or
-          isdst=0 otherwise.
+       Dates are in yyyy-mm-dd format and times are in 24-hour hh:mm:ss format
+       where hh<24.  Times are in local time immediately after the transition.
+       A time interval description consists of a UT offset in signed +-hhmmss
+       format, a time zone abbreviation, and an isdst flag.  An abbreviation
+       that equals the UT offset is omitted; other abbreviations are double-
+       quoted strings unless they consist of one or more alphabetic
+       characters.  An isdst flag is omitted for standard time, and otherwise
+       is a decimal integer that is unsigned and positive (typically 1) for
+       daylight saving time and negative for unknown.
 
-     -c [loyear,]hiyear
-          Cut off verbose output near the start of the given
-          year(s).  By default, the program cuts off verbose
-          output near the starts of the years -500 and 2500.
+       In times and in UT offsets with absolute value less than 100 hours, the
+       seconds are omitted if they are zero, and the minutes are also omitted
+       if they are also zero.  Positive UT offsets are east of Greenwich.  The
+       UT offset -00 denotes a UT placeholder in areas where the actual offset
+       is unspecified; by convention, this occurs when the UT offset is zero
+       and the time zone abbreviation begins with "-" or is "zzz".
+
+       In double-quoted strings, escape sequences represent unusual
+       characters.  The escape sequences are \s for space, and \", \\, \f, \n,
+       \r, \t, and \v with their usual meaning in the C programming language.
+       E.g., the double-quoted string ""CET\s\"\\"" represents the character
+       sequence "CET "\".
+
+       Here is an example of the output, with the leading empty line omitted.
+       (This example is shown with tab stops set far enough apart so that the
+       tabbed columns line up.)
+
+         TZ="Pacific/Honolulu"
+         -           -         -103126  LMT
+         1896-01-13  12:01:26  -1030    HST
+         1933-04-30  03        -0930    HDT  1
+         1933-05-21  11        -1030    HST
+         1942-02-09  03        -0930    HWT  1
+         1945-08-14  13:30     -0930    HPT  1
+         1945-09-30  01        -1030    HST
+         1947-06-08  02:30     -10      HST
+
+       Here, local time begins 10 hours, 31 minutes and 26 seconds west of UT,
+       and is a standard time abbreviated LMT.  Immediately after the first
+       transition, the date is 1896-01-13 and the time is 12:01:26, and the
+       following time interval is 10.5 hours west of UT, a standard time
+       abbreviated HST.  Immediately after the second transition, the date is
+       1933-04-30 and the time is 03:00:00 and the following time interval is
+       9.5 hours west of UT, is abbreviated HDT, and is daylight saving time.
+       Immediately after the last transition the date is 1947-06-08 and the
+       time is 02:30:00, and the following time interval is 10 hours west of
+       UT, a standard time abbreviated HST.
+
+       Here are excerpts from another example:
+
+         TZ="Europe/Astrakhan"
+         -           -         +031212  LMT
+         1924-04-30  23:47:48  +03
+         1930-06-21  01        +04
+         1981-04-01  01        +05           1
+         1981-09-30  23        +04
+         ...
+         2014-10-26  01        +03
+         2016-03-27  03        +04
+
+       This time zone is east of UT, so its UT offsets are positive.  Also,
+       many of its time zone abbreviations are omitted since they duplicate
+       the text of the UT offset.
 
 LIMITATIONS
-     The -v option may not be used on systems with floating-point
-     time_t values that are neither float nor double.
+       Time discontinuities are found by sampling the results returned by
+       localtime(3) at twelve-hour intervals.  This works in all real-world
+       cases; one can construct artificial time zones for which this fails.
 
-     Time discontinuities are found by sampling the results
-     returned by localtime at twelve-hour intervals.  This works
-     in all real-world cases; one can construct artificial time
-     zones for which this fails.
+       In the -v and -V output, "UT" denotes the value returned by gmtime(3),
+       which uses UTC for modern timestamps and some other UT flavor for
+       timestamps that predate the introduction of UTC.  No attempt is
+       currently made to have the output use "UTC" for newer and "UT" for
+       older timestamps, partly because the exact date of the introduction of
+       UTC is problematic.
 
 SEE ALSO
-     newctime(3), tzfile(5), zic(8)
+       tzfile(5), zic(8)
+
+                                                                      ZDUMP(8)