1ZDUMP(8)                  Linux System Administration                 ZDUMP(8)
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NAME

6       zdump - timezone dumper
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SYNOPSIS

9       zdump [ option ... ] [ timezone ... ]
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DESCRIPTION

12       The zdump program prints the current time in each timezone named on the
13       command line.
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OPTIONS

16       --version
17              Output version information and exit.
18
19       --help Output short usage message and exit.
20
21       -i     Output a description of time intervals.  For  each  timezone  on
22              the  command  line, output an interval-format description of the
23              timezone.  See “INTERVAL FORMAT” below.
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25       -v     Output a verbose description of time intervals.  For each  time‐
26              zone  on the command line, print the time at the lowest possible
27              time value, the time one day  after  the  lowest  possible  time
28              value,  the times both one second before and exactly at each de‐
29              tected time discontinuity, the time at one  day  less  than  the
30              highest  possible time value, and the time at the highest possi‐
31              ble time value.  Each line is followed by  isdst=D  where  D  is
32              positive,  zero, or negative depending on whether the given time
33              is daylight saving time, standard time, or an unknown time type,
34              respectively.   Each  line  is  also followed by gmtoff=N if the
35              given local time is known to be N seconds east of Greenwich.
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37       -V     Like -v, except omit the times relative to the extreme time val‐
38              ues.  This generates output that is easier to compare to that of
39              implementations with different time representations.
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41       -c [loyear,]hiyear
42              Cut off interval output at the given year(s).  Cutoff times  are
43              computed  using the proleptic Gregorian calendar with year 0 and
44              with Universal Time (UT) ignoring leap seconds.  Cutoffs are  at
45              the  start  of each year, where the lower-bound timestamp is ex‐
46              clusive and the upper is inclusive; for  example,  -c  1970,2070
47              selects  transitions after 1970-01-01 00:00:00 UTC and on or be‐
48              fore 2070-01-01 00:00:00 UTC.  The default cutoff is -500,2500.
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50       -t [lotime,]hitime
51              Cut off interval output at the given time(s), given  in  decimal
52              seconds  since  1970-01-01  00:00:00  Coordinated Universal Time
53              (UTC).  The timezone determines whether the count includes  leap
54              seconds.   As with -c, the cutoff's lower bound is exclusive and
55              its upper bound is inclusive.
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INTERVAL FORMAT

58       The interval format is a compact text representation that  is  intended
59       to  be both human- and machine-readable.  It consists of an empty line,
60       then a line “TZ=string” where string is a double-quoted  string  giving
61       the timezone, a second line “- - interval” describing the time interval
62       before the first transition if any, and zero or  more  following  lines
63date  time  interval”, one line for each transition time and following
64       interval.  Fields are separated by single tabs.
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66       Dates are in yyyy-mm-dd format and times are in 24-hour hh:mm:ss format
67       where hh<24.  Times are in local time immediately after the transition.
68       A time interval description consists of a UT offset in  signed  ±hhmmss
69       format,  a  time zone abbreviation, and an isdst flag.  An abbreviation
70       that equals the UT offset is omitted; other abbreviations  are  double-
71       quoted  strings  unless  they consist of one or more alphabetic charac‐
72       ters.  An isdst flag is omitted for standard time, and otherwise  is  a
73       decimal  integer  that  is unsigned and positive (typically 1) for day‐
74       light saving time and negative for unknown.
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76       In times and in UT offsets with absolute value less than 100 hours, the
77       seconds  are omitted if they are zero, and the minutes are also omitted
78       if they are also zero.  Positive UT offsets are east of Greenwich.  The
79       UT offset -00 denotes a UT placeholder in areas where the actual offset
80       is unspecified; by convention, this occurs when the UT offset  is  zero
81       and the time zone abbreviation begins with “-” or is “zzz”.
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83       In  double-quoted  strings,  escape sequences represent unusual charac‐
84       ters.  The escape sequences are \s for space, and \", \\, \f,  \n,  \r,
85       \t,  and  \v  with  their  usual meaning in the C programming language.
86       E.g., the double-quoted string “"CET\s\"\\"” represents  the  character
87       sequence “CET "\”.
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89       Here  is an example of the output, with the leading empty line omitted.
90       (This example is shown with tab stops set far enough apart so that  the
91       tabbed columns line up.)
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93         TZ="Pacific/Honolulu"
94         -           -         -103126  LMT
95         1896-01-13  12:01:26  -1030    HST
96         1933-04-30  03        -0930    HDT  1
97         1933-05-21  11        -1030    HST
98         1942-02-09  03        -0930    HWT  1
99         1945-08-14  13:30     -0930    HPT  1
100         1945-09-30  01        -1030    HST
101         1947-06-08  02:30     -10      HST
102
103       Here, local time begins 10 hours, 31 minutes and 26 seconds west of UT,
104       and is a standard time abbreviated LMT.  Immediately  after  the  first
105       transition,  the  date  is 1896-01-13 and the time is 12:01:26, and the
106       following time interval is 10.5 hours west of UT, a standard  time  ab‐
107       breviated  HST.   Immediately  after the second transition, the date is
108       1933-04-30 and the time is 03:00:00 and the following time interval  is
109       9.5  hours west of UT, is abbreviated HDT, and is daylight saving time.
110       Immediately after the last transition the date is  1947-06-08  and  the
111       time  is  02:30:00, and the following time interval is 10 hours west of
112       UT, a standard time abbreviated HST.
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114       Here are excerpts from another example:
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116         TZ="Europe/Astrakhan"
117         -           -         +031212  LMT
118         1924-04-30  23:47:48  +03
119         1930-06-21  01        +04
120         1981-04-01  01        +05           1
121         1981-09-30  23        +04
122         ...
123         2014-10-26  01        +03
124         2016-03-27  03        +04
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126       This time zone is east of UT, so its UT offsets  are  positive.   Also,
127       many  of  its  time zone abbreviations are omitted since they duplicate
128       the text of the UT offset.
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LIMITATIONS

131       Time discontinuities are found by sampling the results returned by  lo‐
132       caltime  at twelve-hour intervals.  This works in all real-world cases;
133       one can construct artificial time zones for which this fails.
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135       In the -v and -V output, “UT” denotes the value returned by  gmtime(3),
136       which uses UTC for modern timestamps and some other UT flavor for time‐
137       stamps that predate the introduction of UTC.  No attempt  is  currently
138       made  to  have  the output use “UTC” for newer and “UT” for older time‐
139       stamps, partly because the exact date of the  introduction  of  UTC  is
140       problematic.
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SEE ALSO

143       tzfile(5), zic(8)
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COLOPHON

146       This  page  is  part of release 5.13 of the Linux man-pages project.  A
147       description of the project, information about reporting bugs,  and  the
148       latest     version     of     this    page,    can    be    found    at
149       https://www.kernel.org/doc/man-pages/.
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153                                  2020-04-27                          ZDUMP(8)
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