1ZDUMP(8) Linux System Administration ZDUMP(8)
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6 zdump - timezone dumper
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9 zdump [ option ... ] [ timezone ... ]
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12 The zdump program prints the current time in each timezone named on the
13 command line.
14
16 --version
17 Output version information and exit.
18 --help Output short usage message and exit.
20 -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.
24 -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
29 detected 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.
36 -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.
40 -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
46 exclusive and the upper is inclusive; for example, -c 1970,2070
47 selects transitions after 1970-01-01 00:00:00 UTC and on or
48 before 2070-01-01 00:00:00 UTC. The default cutoff is
49 -500,2500.
50 -t [lotime,]hitime
52 Cut off interval output at the given time(s), given in decimal
53 seconds since 1970-01-01 00:00:00 Coordinated Universal Time
54 (UTC). The timezone determines whether the count includes leap
55 seconds. As with -c, the cutoff's lower bound is exclusive and
56 its upper bound is inclusive.
57
59 The interval format is a compact text representation that is intended
60 to be both human- and machine-readable. It consists of an empty line,
61 then a line “TZ=string” where string is a double-quoted string giving
62 the timezone, a second line “- - interval” describing the time interval
63 before the first transition if any, and zero or more following lines
64 “date time interval”, one line for each transition time and following
65 interval. Fields are separated by single tabs.
66 Dates are in yyyy-mm-dd format and times are in 24-hour hh:mm:ss format
68 where hh<24. Times are in local time immediately after the transition.
69 A time interval description consists of a UT offset in signed ±hhmmss
70 format, a time zone abbreviation, and an isdst flag. An abbreviation
71 that equals the UT offset is omitted; other abbreviations are double-
72 quoted strings unless they consist of one or more alphabetic charac‐
73 ters. An isdst flag is omitted for standard time, and otherwise is a
74 decimal integer that is unsigned and positive (typically 1) for day‐
75 light saving time and negative for unknown.
76 In times and in UT offsets with absolute value less than 100 hours, the
78 seconds are omitted if they are zero, and the minutes are also omitted
79 if they are also zero. Positive UT offsets are east of Greenwich. The
80 UT offset -00 denotes a UT placeholder in areas where the actual offset
81 is unspecified; by convention, this occurs when the UT offset is zero
82 and the time zone abbreviation begins with “-” or is “zzz”.
83 In double-quoted strings, escape sequences represent unusual charac‐
85 ters. The escape sequences are \s for space, and \", \\, \f, \n, \r,
86 \t, and \v with their usual meaning in the C programming language.
87 E.g., the double-quoted string “"CET\s\"\\"” represents the character
88 sequence “CET "\”.
89 Here is an example of the output, with the leading empty line omitted.
91 (This example is shown with tab stops set far enough apart so that the
92 tabbed columns line up.)
93 TZ="Pacific/Honolulu"
95 - - -103126 LMT
96 1896-01-13 12:01:26 -1030 HST
97 1933-04-30 03 -0930 HDT 1
98 1933-05-21 11 -1030 HST
99 1942-02-09 03 -0930 HWT 1
100 1945-08-14 13:30 -0930 HPT 1
101 1945-09-30 01 -1030 HST
102 1947-06-08 02:30 -10 HST
103 Here, local time begins 10 hours, 31 minutes and 26 seconds west of UT,
105 and is a standard time abbreviated LMT. Immediately after the first
106 transition, the date is 1896-01-13 and the time is 12:01:26, and the
107 following time interval is 10.5 hours west of UT, a standard time
108 abbreviated HST. Immediately after the second transition, the date is
109 1933-04-30 and the time is 03:00:00 and the following time interval is
110 9.5 hours west of UT, is abbreviated HDT, and is daylight saving time.
111 Immediately after the last transition the date is 1947-06-08 and the
112 time is 02:30:00, and the following time interval is 10 hours west of
113 UT, a standard time abbreviated HST.
114 Here are excerpts from another example:
116 TZ="Europe/Astrakhan"
118 - - +031212 LMT
119 1924-04-30 23:47:48 +03
120 1930-06-21 01 +04
121 1981-04-01 01 +05 1
122 1981-09-30 23 +04
123 ...
124 2014-10-26 01 +03
125 2016-03-27 03 +04
126 This time zone is east of UT, so its UT offsets are positive. Also,
128 many of its time zone abbreviations are omitted since they duplicate
129 the text of the UT offset.
130
132 Time discontinuities are found by sampling the results returned by
133 localtime at twelve-hour intervals. This works in all real-world
134 cases; one can construct artificial time zones for which this fails.
135 In the -v and -V output, “UT” denotes the value returned by gmtime(3),
137 which uses UTC for modern timestamps and some other UT flavor for time‐
138 stamps that predate the introduction of UTC. No attempt is currently
139 made to have the output use “UTC” for newer and “UT” for older time‐
140 stamps, partly because the exact date of the introduction of UTC is
141 problematic.
142
144 tzfile(5), zic(8)
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147 This page is part of release 5.07 of the Linux man-pages project. A
148 description of the project, information about reporting bugs, and the
149 latest version of this page, can be found at
150 https://www.kernel.org/doc/man-pages/.
151 2020-04-27 ZDUMP(8)