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Fix breakage in new-in-7.3 timetz_zone() function: was giving random
results due to doing arithmetic on uninitialized values. Add some documentation about the AT TIME ZONE construct. Update some other date/time documentation that seemed out of date for 7.3.
This commit is contained in:
Tom Lane
parent
ca1d1b79ab
commit
75394d3f5b
@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.108 2002/11/15 03:11:15 momjian Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.109 2002/11/21 23:31:20 tgl Exp $
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-->
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<chapter id="datatype">
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@ -1569,20 +1569,32 @@ SELECT b, char_length(b) FROM test2;
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<secondary>data type</secondary>
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</indexterm>
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<indexterm>
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<primary>timestamp with time zone</primary>
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<secondary>data type</secondary>
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</indexterm>
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<indexterm>
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<primary>timestamp without time zone</primary>
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<secondary>data type</secondary>
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</indexterm>
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<para>
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Time stamp types exist as <type>timestamp [
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(<replaceable>p</replaceable>) ]</type>, <type>timestamp [
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The time stamp types are <type>timestamp [
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(<replaceable>p</replaceable>) ] without time zone</type> and
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<type>timestamp [ (<replaceable>p</replaceable>) ] without time
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zone</type>. A plain <type>timestamp</type> is equivalent to
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<type>timestamp without timezone</type>.
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<type>timestamp [ (<replaceable>p</replaceable>) ] with time
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zone</type>. Writing just <type>timestamp</type> is equivalent to
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<type>timestamp without time zone</type>.
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</para>
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<note>
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<para>
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Prior to <productname>PostgreSQL</productname> 7.3, writing just
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<type>timestamp</type> was equivalent to <type>timestamp with time
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zone</type>. This was changed for SQL spec compliance.
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</para>
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</note>
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<para>
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Valid input for the time stamp types consists of a concatenation
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of a date and a time, followed by an optional
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@ -1615,11 +1627,38 @@ January 8 04:05:06 1999 PST
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<para>
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For <type>timestamp without time zone</type>, any explicit time
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zone specified in the input is silently swallowed. That is, the
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zone specified in the input is silently ignored. That is, the
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resulting date/time value is derived from the explicit date/time
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fields in the input value, and is not adjusted for time zone.
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</para>
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<para>
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For <type>timestamp with time zone</type>, the internally stored
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value is always in UTC (GMT). An input value that has an explicit
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time zone specified is converted to UTC using the appropriate offset
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for that time zone. If no time zone is stated in the input string,
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then it is assumed to be in the time zone indicated by the system's
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<varname>TimeZone</> parameter, and is converted to UTC using the
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offset for the <varname>TimeZone</> zone.
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</para>
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<para>
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When a <type>timestamp with time
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zone</type> value is output, it is always converted from UTC to the
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current <varname>TimeZone</> zone, and displayed as local time in that
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zone. To see the time in another time zone, either change
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<varname>TimeZone</> or use the <literal>AT TIME ZONE</> construct
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(see <xref linkend="functions-datetime-zoneconvert">).
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</para>
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<para>
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Conversions between <type>timestamp without time zone</type> and
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<type>timestamp with time zone</type> normally assume that the
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<type>timestamp without time zone</type> value should be taken or given
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as <varname>TimeZone</> local time. A different zone reference can
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be specified for the conversion using <literal>AT TIME ZONE</>.
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</para>
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<table tocentry="1" id="datatype-timezone-table">
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<title>Time Zone Input</title>
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<tgroup cols="2">
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@ -1707,24 +1746,28 @@ January 8 04:05:06 1999 PST
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<para>
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The following <acronym>SQL</acronym>-compatible functions can be
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used as date or time
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input for the corresponding data type: <literal>CURRENT_DATE</literal>,
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values for the corresponding data type: <literal>CURRENT_DATE</literal>,
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<literal>CURRENT_TIME</literal>,
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<literal>CURRENT_TIMESTAMP</literal>. The latter two accept an
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optional precision specification. (See also <xref linkend="functions-datetime">.)
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optional precision specification. (See also <xref linkend="functions-datetime-current">.)
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</para>
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<para>
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<productname>PostgreSQL</productname> also supports several
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special constants for convenience, shown in <xref
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linkend="datatype-datetime-special-table">.
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special date/time input values for convenience, as shown in <xref
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linkend="datatype-datetime-special-table">. The values
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<literal>infinity</literal> and <literal>-infinity</literal>
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are specially represented inside the system and will be displayed
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the same way; but the others are simply notational shorthands
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that will be converted to ordinary date/time values when read.
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</para>
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<table id="datatype-datetime-special-table">
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<title>Special Date/Time Constants</title>
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<title>Special Date/Time Inputs</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Constant</entry>
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<entry>Input string</entry>
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<entry>Description</entry>
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</row>
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</thead>
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@ -1735,15 +1778,13 @@ January 8 04:05:06 1999 PST
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</row>
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<row>
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<entry><literal>infinity</literal></entry>
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<entry>later than other valid times</entry>
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<entry>later than all other timestamps (not available for
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type <type>date</>)</entry>
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</row>
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<row>
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<entry><literal>-infinity</literal></entry>
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<entry>earlier than other valid times</entry>
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</row>
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<row>
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<entry><literal>invalid</literal></entry>
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<entry>illegal entry</entry>
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<entry>earlier than all other timestamps (not available for
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type <type>date</>)</entry>
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</row>
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<row>
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<entry><literal>now</literal></entry>
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@ -1962,13 +2003,21 @@ January 8 04:05:06 1999 PST
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</para>
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<para>
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There are several ways to affect the time-zone behavior:
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There are several ways to select the time zone used by the server:
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<itemizedlist>
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<listitem>
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<para>
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The <envar>TZ</envar> environment variable on the server host
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is used by the server as the default time zone.
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is used by the server as the default time zone, if no other is
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specified.
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</para>
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</listitem>
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<listitem>
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<para>
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The <varname>timezone</varname> configuration parameter can be
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set in <filename>postgresql.conf</>.
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</para>
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</listitem>
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@ -1987,18 +2036,6 @@ January 8 04:05:06 1999 PST
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sets the time zone for the session.
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</para>
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</listitem>
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<listitem>
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<para>
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The construct
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<programlisting>
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<replaceable>timestamp</replaceable> AT TIME ZONE '<replaceable>zone</replaceable>'
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</programlisting>
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where <replaceable>zone</replaceable> can be specified as a
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text time zone (e.g., <literal>'PST'</literal>) or as an
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interval (e.g., <literal>INTERVAL '-08:00'</literal>).
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</para>
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</listitem>
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</itemizedlist>
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</para>
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@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.130 2002/11/11 20:14:02 petere Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.131 2002/11/21 23:31:20 tgl Exp $
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PostgreSQL documentation
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-->
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@ -3549,9 +3549,14 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation>
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<literal>*</literal>, etc.). For formatting functions, refer to
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<xref linkend="functions-formatting">. You should be familiar with
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the background information on date/time data types (see <xref
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linkend="datatype-datetime">). The date/time operators described
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below behave similarly for types involving time zones as well as
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those without.
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linkend="datatype-datetime">).
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</para>
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<para>
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All the functions and operators described below that take time or timestamp
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inputs actually come in two variants: one that takes time or timestamp
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with time zone, and one that takes time or timestamp without time zone.
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For brevity, these variants are not shown separately.
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</para>
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<table id="operators-datetime-table">
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@ -3771,7 +3776,7 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation>
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<row>
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<entry><function>now</function>()</entry>
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<entry><type>timestamp</type></entry>
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<entry><type>timestamp with time zone</type></entry>
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<entry>Current date and time (equivalent to
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<function>current_timestamp</function>); see <xref
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linkend="functions-datetime-current">
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@ -3898,8 +3903,8 @@ SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');
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<listitem>
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<para>
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For <type>date</type> and <type>timestamp</type> values, the
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number of seconds since 1970-01-01 00:00:00-00 (Result may be
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negative.); for <type>interval</type> values, the total number
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number of seconds since 1970-01-01 00:00:00-00 (can be negative);
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for <type>interval</type> values, the total number
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of seconds in the interval
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</para>
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@ -4122,12 +4127,12 @@ SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40');
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<para>
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The <function>date_part</function> function is modeled on the traditional
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<productname>Ingres</productname> equivalent to the
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<acronym>SQL</acronym>-function <function>extract</function>:
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<acronym>SQL</acronym>-standard function <function>extract</function>:
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<synopsis>
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date_part('<replaceable>field</replaceable>', <replaceable>source</replaceable>)
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</synopsis>
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Note that here the <replaceable>field</replaceable> value needs to
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be a string. The valid field values for
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Note that here the <replaceable>field</replaceable> parameter needs to
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be a string value, not a name. The valid field values for
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<function>date_part</function> are the same as for
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<function>extract</function>.
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</para>
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@ -4192,6 +4197,95 @@ SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');
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</para>
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</sect2>
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<sect2 id="functions-datetime-zoneconvert">
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<title><function>AT TIME ZONE</function></title>
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<indexterm>
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<primary>timezone</primary>
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<secondary>conversion</secondary>
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</indexterm>
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<para>
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The <function>AT TIME ZONE</function> construct allows conversions
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of timestamps to different timezones.
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</para>
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<table id="functions-datetime-zoneconvert-table">
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<title>AT TIME ZONE Variants</title>
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<tgroup cols="3">
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<thead>
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<row>
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<entry>Expression</entry>
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<entry>Returns</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>
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<type>timestamp without time zone</type>
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<literal>AT TIME ZONE</literal>
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<replaceable>zone</>
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</entry>
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<entry><type>timestamp with time zone</type></entry>
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<entry>Convert local time in given timezone to UTC</entry>
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</row>
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<row>
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<entry>
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<type>timestamp with time zone</type>
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<literal>AT TIME ZONE</literal>
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<replaceable>zone</>
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</entry>
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<entry><type>timestamp without time zone</type></entry>
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<entry>Convert UTC to local time in given timezone</entry>
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</row>
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<row>
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<entry>
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<type>time with time zone</type>
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<literal>AT TIME ZONE</literal>
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<replaceable>zone</>
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</entry>
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<entry><type>time with time zone</type></entry>
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<entry>Convert local time across timezones</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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In these expressions, the desired time <replaceable>zone</> can be
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specified either as a text string (e.g., <literal>'PST'</literal>)
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or as an interval (e.g., <literal>INTERVAL '-08:00'</literal>).
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</para>
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<para>
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Examples (supposing that <varname>TimeZone</> is <literal>PST8PDT</>):
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<screen>
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SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'MST';
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<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 19:38:40-08</computeroutput>
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SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'MST';
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<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 18:38:40</computeroutput>
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</screen>
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The first example takes a zone-less timestamp and interprets it as MST time
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(GMT-7) to produce a UTC timestamp, which is then rotated to PST (GMT-8)
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for display. The second example takes a timestamp specified in EST
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(GMT-5) and converts it to local time in MST (GMT-7).
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</para>
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<para>
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The function <function>timezone</function>(<replaceable>zone</>,
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<replaceable>timestamp</>) is equivalent to the SQL-compliant construct
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<replaceable>timestamp</> <literal>AT TIME ZONE</literal>
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<replaceable>zone</>.
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</para>
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</sect2>
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<sect2 id="functions-datetime-current">
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<title>Current Date/Time</title>
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@ -4219,6 +4313,16 @@ LOCALTIMESTAMP
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LOCALTIME ( <replaceable>precision</replaceable> )
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LOCALTIMESTAMP ( <replaceable>precision</replaceable> )
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</synopsis>
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</para>
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<para>
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<function>CURRENT_TIME</function> and
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<function>CURRENT_TIMESTAMP</function> deliver values with time zone;
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<function>LOCALTIME</function> and
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<function>LOCALTIMESTAMP</function> deliver values without time zone.
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</para>
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<para>
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<function>CURRENT_TIME</function>,
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<function>CURRENT_TIMESTAMP</function>,
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<function>LOCALTIME</function>, and
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/date.c,v 1.73 2002/09/21 19:52:41 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/date.c,v 1.74 2002/11/21 23:31:20 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -2013,7 +2013,6 @@ timetz_zone(PG_FUNCTION_ARGS)
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text *zone = PG_GETARG_TEXT_P(0);
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TimeTzADT *time = PG_GETARG_TIMETZADT_P(1);
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TimeTzADT *result;
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TimeADT time1;
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int tz;
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int type,
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val;
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@ -2040,15 +2039,17 @@ timetz_zone(PG_FUNCTION_ARGS)
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{
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tz = val * 60;
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#ifdef HAVE_INT64_TIMESTAMP
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time1 = (time->time - ((time->zone + tz) * INT64CONST(1000000)));
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result->time -= ((result->time / time1) * time1);
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if (result->time < INT64CONST(0))
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result->time = time->time + ((time->zone - tz) * INT64CONST(1000000));
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while (result->time < INT64CONST(0))
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result->time += INT64CONST(86400000000);
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while (result->time >= INT64CONST(86400000000))
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result->time -= INT64CONST(86400000000);
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#else
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time1 = (time->time - time->zone + tz);
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TMODULO(result->time, time1, 86400e0);
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if (result->time < 0)
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result->time = time->time + (time->zone - tz);
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while (result->time < 0)
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result->time += 86400;
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while (result->time >= 86400)
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result->time -= 86400;
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#endif
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result->zone = tz;
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@ -2087,13 +2088,13 @@ timetz_izone(PG_FUNCTION_ARGS)
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result = (TimeTzADT *) palloc(sizeof(TimeTzADT));
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#ifdef HAVE_INT64_TIMESTAMP
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result->time = (time->time + ((time->zone - tz) * INT64CONST(1000000)));
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result->time = time->time + ((time->zone - tz) * INT64CONST(1000000));
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while (result->time < INT64CONST(0))
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result->time += INT64CONST(86400000000);
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while (result->time >= INT64CONST(86400000000))
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result->time -= INT64CONST(86400000000);
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#else
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result->time = (time->time + (time->zone - tz));
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result->time = time->time + (time->zone - tz);
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while (result->time < 0)
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result->time += 86400;
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while (result->time >= 86400)
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