reference/datetime/functions/strtotime.xml
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type>int</type><methodname>strtotime</methodname>
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<methodparam><type>string</type><parameter>time</parameter></methodparam>
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<methodparam choice="opt"><type>int</type><parameter>now</parameter><initializer>time()</initializer></methodparam>
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<type class="union"><type>int</type><type>false</type></type><methodname>strtotime</methodname>
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<methodparam><type>string</type><parameter>datetime</parameter></methodparam>
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<methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>baseTimestamp</parameter><initializer>&null;</initializer></methodparam>
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</methodsynopsis>
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<simpara>
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The function expects to be given a string containing an English date format
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and will try to parse that format into a Unix timestamp (the number of
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seconds since January 1 1970 00:00:00 UTC), relative to the timestamp given
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in <parameter>now</parameter>, or the current time if
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<parameter>now</parameter> is not supplied.
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in <parameter>baseTimestamp</parameter>, or the current time if
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<parameter>baseTimestamp</parameter> is not supplied. The date string parsing
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is defined in <link linkend="datetime.formats">Date and Time Formats</link>, and
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has several subtle considerations. Reviewing the full details there is strongly
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recommended.
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</simpara>
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<warning>
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<para>
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The Unix timestamp that this function returns does not contain information
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about time zones. In order to do calculations with date/time information,
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you should use the more capable <classname>DateTimeImmutable</classname>.
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</para>
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</warning>
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<para>
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Each parameter of this function uses the default time zone unless a
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time zone is specified in that parameter. Be careful not to use
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>time</parameter></term>
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<term><parameter>datetime</parameter></term>
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<listitem>
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<para>&date.formats.parameter;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>now</parameter></term>
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<term><parameter>baseTimestamp</parameter></term>
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<listitem>
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<para>
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The timestamp which is used as a base for the calculation of relative
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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Returns a timestamp on success, &false; otherwise. Previous to PHP 5.1.0,
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this function would return <literal>-1</literal> on failure.
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Returns a timestamp on success, &false; otherwise.
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</para>
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</refsect1>
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</thead>
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<tbody>
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<row>
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<entry>5.3.0</entry>
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<entry>
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Prior to PHP 5.3.0, relative time formats supplied to the
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<parameter>time</parameter> argument of <function>strtotime</function>
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such as <literal>this week</literal>, <literal>previous week</literal>,
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<literal>last week</literal>, and <literal>next week</literal> were
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interpreted to mean a 7 day period relative to the current date/time, rather
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than a week period of <literal>Monday</literal> through <literal>Sunday</literal>.
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</entry>
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</row>
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<row>
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<entry>5.3.0</entry>
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<entry>
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Prior to PHP 5.3.0, <literal>24:00</literal> was not a valid format and
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<function>strtotime</function> returned &false;.
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</entry>
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</row>
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<row>
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<entry>5.2.7</entry>
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<entry>8.0.0</entry>
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<entry>
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In PHP 5 prior to 5.2.7, requesting a given occurrence of a
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given weekday in a month where that weekday was the first day
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of the month would incorrectly add one week to the returned
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timestamp. This has been corrected in 5.2.7 and later
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versions.
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</entry>
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</row>
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<row>
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<entry>5.1.0</entry>
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<entry>
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Now returns &false; on failure, instead
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of <literal>-1</literal>.
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</entry>
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</row>
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&date.timezone.errors.changelog;
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<row>
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<entry>5.0.2</entry>
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<entry>
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In PHP 5 up to 5.0.2, <literal>"now"</literal> and other
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relative times are wrongly computed from today's
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midnight. This differs from other versions where it is
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correctly computed from current time.
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</entry>
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</row>
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<row>
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<entry>5.0.0</entry>
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<entry>
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Microseconds began to be allowed, but they are ignored.
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<parameter>baseTimestamp</parameter> is nullable now.
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</entry>
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</row>
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</tbody>
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<?php
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$str = 'Not Good';
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// previous to PHP 5.1.0 you would compare with -1, instead of false
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if (($timestamp = strtotime($str)) === false) {
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echo "The string ($str) is bogus";
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} else {
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&reftitle.notes;
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<note>
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<para>
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"Relative" date in this case also means that if a particular component
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of the date/time stamp is not provided, it will be taken verbatim from
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the <parameter>baseTimestamp</parameter>. That is, <code>strtotime('February')</code>,
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if run on the 31st of May 2022, will be interpreted as <literal>31 February 2022</literal>,
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which will overflow into a timestamp on <literal>3 March</literal>.
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(In a leap year, it would be <literal>2 March</literal>.) Using
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<code>strtotime('1 February')</code> or <code>strtotime('first day of February')</code>
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would avoid that problem.
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</para>
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</note>
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<note>
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<para>
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If the number of the year is specified in a two digit format, the values
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between 00-69 are mapped to 2000-2069 and 70-99 to 1970-1999. See the notes
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below for possible differences on 32bit systems (possible dates might end on
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a 32-bit signed integer.)
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</para>
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<para>
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Prior to PHP 5.1.0, not all platforms support negative timestamps, therefore
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your date range may be limited to no earlier than the Unix epoch. This
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means that e.g. dates prior to Jan 1, 1970 will not work on Windows,
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some Linux distributions, and a few other operating systems.
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</para>
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<para>
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For 64-bit versions of PHP, the valid range of a timestamp is effectively
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infinite, as 64 bits can represent approximately 293 billion years in either
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direction.
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</note>
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<note>
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<para>
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Dates in the <literal>m/d/y</literal> or <literal>d-m-y</literal> formats
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are disambiguated by looking at the separator between the various
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components: if the separator is a slash (<literal>/</literal>), then the
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American <literal>m/d/y</literal> is assumed; whereas if the separator is a
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dash (<literal>-</literal>) or a dot (<literal>.</literal>), then the
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European <literal>d-m-y</literal> format is assumed.
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If, however, the year is given in a two digit format and the separator is a
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dash (<literal>-</literal>, the date string is parsed as
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<literal>y-m-d</literal>.
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</para>
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<para>
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To avoid potential ambiguity, it's best to use ISO 8601
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(<literal>YYYY-MM-DD</literal>) dates or
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<methodname>DateTime::createFromFormat</methodname> when possible.
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</para>
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</note>
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<note>
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<para>
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Using this function for mathematical operations is not advisable.
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It is better to use <methodname>DateTime::add</methodname> and
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<methodname>DateTime::sub</methodname> in PHP 5.3 and later, or
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<methodname>DateTime::modify</methodname> in PHP 5.2.
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<methodname>DateTime::sub</methodname>.
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</para>
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</note>
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</refsect1>
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><classname>DateTimeImmutable</classname></member>
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<member><methodname>DateTimeImmutable::createFromFormat</methodname></member>
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<member><link linkend="datetime.formats">Date and Time Formats</link></member>
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<member><methodname>DateTime::createFromFormat</methodname></member>
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<member><function>checkdate</function></member>
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<member><function>strptime</function></member>
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</simplelist>
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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