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1 zdump(8) System Manager's Manual zdump(8)
2
3 NAME
4 zdump - timezone dumper
5
6 SYNOPSIS
7 zdump [ option ... ] [ timezone ... ]
8
9 DESCRIPTION
10 The zdump program prints the current time in each timezone named on the
11 command line.
12
13 OPTIONS
14 --version
15 Output version information and exit.
16
17 --help Output short usage message and exit.
18
19 -i Output a description of time intervals. For each timezone on
20 the command line, output an interval-format description of the
21 timezone. See "INTERVAL FORMAT" below.
22
23 -v Output a verbose description of time intervals. For each
24 timezone on the command line, print the times at the two extreme
25 time values, the times (if present) at and just beyond the
26 boundaries of years that localtime(3) and gmtime(3) can
27 represent, and the times both one second before and exactly at
28 each detected time discontinuity. Each line is followed by
29 isdst=D where D is positive, zero, or negative depending on
30 whether the given time is daylight saving time, standard time,
31 or an unknown time type, respectively. Each line is also
32 followed by gmtoff=N if the given local time is known to be N
33 seconds east of Greenwich.
34
35 -V Like -v, except omit output concerning extreme time and year
36 values. This generates output that is easier to compare to that
37 of implementations with different time representations.
38
39 -c [loyear,]hiyear
40 Cut off interval output at the given year(s). Cutoff times are
41 computed using the proleptic Gregorian calendar with year 0 and
42 with Universal Time (UT) ignoring leap seconds. Cutoffs are at
43 the start of each year, where the lower-bound timestamp is
44 inclusive and the upper is exclusive; for example, -c 1970,2070
45 selects transitions on or after 1970-01-01 00:00:00 UTC and
46 before 2070-01-01 00:00:00 UTC. The default cutoff is
47 -500,2500.
48
49 -t [lotime,]hitime
50 Cut off interval output at the given time(s), given in decimal
51 seconds since 1970-01-01 00:00:00 Coordinated Universal Time
52 (UTC). The timezone determines whether the count includes leap
53 seconds. As with -c, the cutoff's lower bound is inclusive and
54 its upper bound is exclusive.
55
56 INTERVAL FORMAT
57 The interval format is a compact text representation that is intended
58 to be both human- and machine-readable. It consists of an empty line,
59 then a line "TZ=string" where string is a double-quoted string giving
60 the timezone, a second line "- - interval" describing the time interval
61 before the first transition if any, and zero or more following lines
62 "date time interval", one line for each transition time and following
63 interval. Fields are separated by single tabs.
64
65 Dates are in yyyy-mm-dd format and times are in 24-hour hh:mm:ss format
66 where hh<24. Times are in local time immediately after the transition.
67 A time interval description consists of a UT offset in signed +-hhmmss
68 format, a time zone abbreviation, and an isdst flag. An abbreviation
69 that equals the UT offset is omitted; other abbreviations are double-
70 quoted strings unless they consist of one or more alphabetic
71 characters. An isdst flag is omitted for standard time, and otherwise
72 is a decimal integer that is unsigned and positive (typically 1) for
73 daylight saving time and negative for unknown.
74
75 In times and in UT offsets with absolute value less than 100 hours, the
76 seconds are omitted if they are zero, and the minutes are also omitted
77 if they are also zero. Positive UT offsets are east of Greenwich. The
78 UT offset -00 denotes a UT placeholder in areas where the actual offset
79 is unspecified; by convention, this occurs when the UT offset is zero
80 and the time zone abbreviation begins with "-" or is "zzz".
81
82 In double-quoted strings, escape sequences represent unusual
83 characters. The escape sequences are \s for space, and \", \\, \f, \n,
84 \r, \t, and \v with their usual meaning in the C programming language.
85 E.g., the double-quoted string ""CET\s\"\\"" represents the character
86 sequence "CET "\".
87
88 Here is an example of the output, with the leading empty line omitted.
89 (This example is shown with tab stops set far enough apart so that the
90 tabbed columns line up.)
91
92 TZ="Pacific/Honolulu"
93 - - -103126 LMT
94 1896-01-13 12:01:26 -1030 HST
95 1933-04-30 03 -0930 HDT 1
96 1933-05-21 11 -1030 HST
97 1942-02-09 03 -0930 HWT 1
98 1945-08-14 13:30 -0930 HPT 1
99 1945-09-30 01 -1030 HST
100 1947-06-08 02:30 -10 HST
101
102 Here, local time begins 10 hours, 31 minutes and 26 seconds west of UT,
103 and is a standard time abbreviated LMT. Immediately after the first
104 transition, the date is 1896-01-13 and the time is 12:01:26, and the
105 following time interval is 10.5 hours west of UT, a standard time
106 abbreviated HST. Immediately after the second transition, the date is
107 1933-04-30 and the time is 03:00:00 and the following time interval is
108 9.5 hours west of UT, is abbreviated HDT, and is daylight saving time.
109 Immediately after the last transition the date is 1947-06-08 and the
110 time is 02:30:00, and the following time interval is 10 hours west of
111 UT, a standard time abbreviated HST.
112
113 Here are excerpts from another example:
114
115 TZ="Europe/Astrakhan"
116 - - +031212 LMT
117 1924-04-30 23:47:48 +03
118 1930-06-21 01 +04
119 1981-04-01 01 +05 1
120 1981-09-30 23 +04
121 ...
122 2014-10-26 01 +03
123 2016-03-27 03 +04
124
125 This time zone is east of UT, so its UT offsets are positive. Also,
126 many of its time zone abbreviations are omitted since they duplicate
127 the text of the UT offset.
128
129 LIMITATIONS
130 Time discontinuities are found by sampling the results returned by
131 localtime(3) at twelve-hour intervals. This works in all real-world
132 cases; one can construct artificial time zones for which this fails.
133
134 In the -v and -V output, "UT" denotes the value returned by gmtime(3),
135 which uses UTC for modern timestamps and some other UT flavor for
136 timestamps that predate the introduction of UTC. No attempt is
137 currently made to have the output use "UTC" for newer and "UT" for
138 older timestamps, partly because the exact date of the introduction of
139 UTC is problematic.
140
141 SEE ALSO
142 tzfile(5), zic(8)
143
144 zdump(8)