316 lines
8.0 KiB
HTML
316 lines
8.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of ZDUMP</TITLE>
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</HEAD><BODY>
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<H1>ZDUMP</H1>
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Section: Linux System Administration (8)<BR>Updated: 2019-03-06<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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zdump - timezone dumper
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>zdump</B>
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[
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<I>option</I>
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... ] [
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<I>timezone</I>
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... ]
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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ds - -
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The
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<B>zdump</B>
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program prints the current time in each
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<I>timezone</I>
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named on the command line.
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<A NAME="lbAE"> </A>
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<H2>OPTIONS</H2>
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<DL COMPACT>
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<DT id="1"><B>version</B>
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<DD>
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Output version information and exit.
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<DT id="2"><B>help</B>
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<DD>
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Output short usage message and exit.
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<DT id="3"><B>i</B>
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<DD>
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Output a description of time intervals. For each
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<I>timezone</I>
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on the command line, output an interval-format description of the
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timezone. See
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below.
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<DT id="4"><B>v</B>
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<DD>
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Output a verbose description of time intervals.
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For each
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<I>timezone</I>
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on the command line,
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print the time at the lowest possible time value,
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the time one day after the lowest possible time value,
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the times both one second before and exactly at
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each detected time discontinuity,
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the time at one day less than the highest possible time value,
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and the time at the highest possible time value.
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Each line is followed by
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<B>isdst=</B><I>D</I>
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where
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<I>D</I>
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is positive, zero, or negative depending on whether
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the given time is daylight saving time, standard time,
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or an unknown time type, respectively.
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Each line is also followed by
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<B>gmtoff=</B><I>N</I>
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if the given local time is known to be
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<I>N</I>
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seconds east of Greenwich.
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<DT id="5"><B>V</B>
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<DD>
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Like
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<B>v</B>,
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except omit the times relative to the extreme time values.
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This generates output that is easier to compare to that of
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implementations with different time representations.
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<DT id="6"><B>c </B><I></I>[<I>loyear</I><B>,</B><I></I>]<I>hiyear</I>
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<DD>
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Cut off interval output at the given year(s).
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Cutoff times are computed using the proleptic Gregorian calendar with year 0
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and with Universal Time (UT) ignoring leap seconds.
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The lower bound is exclusive and the upper is inclusive; for example, a
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<I>loyear</I>
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of 1970 excludes a transition occurring at 1970-01-01 00:00:00 UTC but a
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<I>hiyear</I>
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of 1970 includes the transition.
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The default cutoff is
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<B>500,2500</B>.
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<DT id="7"><B>t </B><I></I>[<I>lotime</I><B>,</B><I></I>]<I>hitime</I>
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<DD>
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Cut off interval output at the given time(s),
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given in decimal seconds since 1970-01-01 00:00:00
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Coordinated Universal Time (UTC).
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The
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<I>timezone</I>
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determines whether the count includes leap seconds.
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As with
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<B>c</B>,
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the cutoff's lower bound is exclusive and its upper bound is inclusive.
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</DL>
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<A NAME="lbAF"> </A>
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<H2>INTERVAL FORMAT</H2>
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The interval format is a compact text representation that is intended
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to be both human- and machine-readable. It consists of an empty line,
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then a line
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where
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<I>string</I>
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is a double-quoted string giving the timezone, a second line
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describing the time interval before the first transition if any, and
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zero or more following lines
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one line for each transition time and following interval. Fields are
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separated by single tabs.
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<P>
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Dates are in
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<I>yyyy</I>-<I>mm</I>-<I>dd</I>
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format and times are in 24-hour
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<I>hh</I>:<I>mm</I>:<I>ss</I>
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format where
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<I>hh</I><24.
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Times are in local time immediately after the transition. A
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time interval description consists of a UT offset in signed
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±<I>hhmmss</I>
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format, a time zone abbreviation, and an isdst flag. An abbreviation
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that equals the UT offset is omitted; other abbreviations are
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double-quoted strings unless they consist of one or more alphabetic
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characters. An isdst flag is omitted for standard time, and otherwise
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is a decimal integer that is unsigned and positive (typically 1) for
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daylight saving time and negative for unknown.
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<P>
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In times and in UT offsets with absolute value less than 100 hours,
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the seconds are omitted if they are zero, and
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the minutes are also omitted if they are also zero. Positive UT
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offsets are east of Greenwich. The UT offset 00 denotes a UT
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placeholder in areas where the actual offset is unspecified; by
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convention, this occurs when the UT offset is zero and the time zone
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abbreviation begins with
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or is
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<P>
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In double-quoted strings, escape sequences represent unusual
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characters. The escape sequences are \s for space, and \", \\,
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\f, \n, \r, \t, and \v with their usual meaning in the C
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programming language. E.g., the double-quoted string
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"
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"CET\s\"\\""
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represents the character sequence "
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CET
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"\"
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.<P>
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Here is an example of the output, with the leading empty line omitted.
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(This example is shown with tab stops set far enough apart so that the
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tabbed columns line up.)
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<PRE>
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TZ="Pacific/Honolulu"
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- - -10:31:26 LMT
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1896-01-13 12:01:26 -10:30 HST
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1933-04-30 03 -09:30 HDT 1
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1933-05-21 11 -10:30 HST
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1942-02-09 03 -09:30 HDT 1
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1945-09-30 01 -10:30 HST
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1947-06-08 02:30 -10 HST
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</PRE>
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Here, local time begins 10 hours, 31 minutes and 26 seconds west of
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UT, and is a standard time abbreviated LMT. Immediately after the
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first transition, the date is 1896-01-13 and the time is 12:01:26, and
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the following time interval is 10.5 hours west of UT, a standard time
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abbreviated HST. Immediately after the second transition, the date is
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1933-04-30 and the time is 03:00:00 and the following time interval is
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9.5 hours west of UT, is abbreviated HDT, and is daylight saving time.
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Immediately after the last transition the date is 1947-06-08 and the
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time is 02:30:00, and the following time interval is 10 hours west of
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UT, a standard time abbreviated HST.
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<P>
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Here are excerpts from another example:
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<PRE>
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TZ="Europe/Astrakhan"
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- - +03:12:12 LMT
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1924-04-30 23:47:48 +03
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1930-06-21 01 +04
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1981-04-01 01 +05 1
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1981-09-30 23 +04
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...
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2014-10-26 01 +03
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2016-03-27 03 +04
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</PRE>
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This time zone is east of UT, so its UT offsets are positive. Also,
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many of its time zone abbreviations are omitted since they duplicate
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the text of the UT offset.
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<A NAME="lbAG"> </A>
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<H2>LIMITATIONS</H2>
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Time discontinuities are found by sampling the results returned by localtime
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at twelve-hour intervals.
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This works in all real-world cases;
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one can construct artificial time zones for which this fails.
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<P>
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In the
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<B>v</B>
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and
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<B>V</B>
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output,
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denotes the value returned by
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<B><A HREF="/cgi-bin/man/man2html?3+gmtime">gmtime</A></B>(3),
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which uses UTC for modern timestamps and some other UT flavor for
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timestamps that predate the introduction of UTC.
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No attempt is currently made to have the output use
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for newer and
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for older timestamps, partly because the exact date of the
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introduction of UTC is problematic.
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<A NAME="lbAH"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?5+tzfile">tzfile</A></B>(5),
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<B><A HREF="/cgi-bin/man/man2html?8+zic">zic</A></B>(8)
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<A NAME="lbAI"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="8"><A HREF="#lbAB">NAME</A><DD>
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<DT id="9"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="10"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="11"><A HREF="#lbAE">OPTIONS</A><DD>
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<DT id="12"><A HREF="#lbAF">INTERVAL FORMAT</A><DD>
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<DT id="13"><A HREF="#lbAG">LIMITATIONS</A><DD>
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<DT id="14"><A HREF="#lbAH">SEE ALSO</A><DD>
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<DT id="15"><A HREF="#lbAI">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:06:19 GMT, March 31, 2021
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</BODY>
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</HTML>
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