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93 lines
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93 lines
3.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<html><head><meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1">
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<title>posix_time::local time adjust Documentation</title>
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<link href="doxygen.css" rel="stylesheet" type="text/css">
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</head>
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<body>
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<a href="../../../index.htm">
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<img align="left" src="../../../c++boost.gif" alt="C++ Boost">
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</a>
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<h1>Local Time Adjustment</h1>
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<p> <p>
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<hr>
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<p>
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<a href="index.html">Overall Index</a> --
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<a href="gregorian.html">Gregorian Index</a> --
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<a href="posix_time.html">Posix Time Index</a>
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<p>
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<font class="bold">Local Time Adjustment</font>
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<p>
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<a href="#header">Header</a> --
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<a href="#classoverview">Class Overview</a> --
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<p>
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<h2><a name="intro">Introduction</a></h2>
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<p>
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A frequent problem in time representation is the conversion between
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various local time systems. In general this is accomplished by
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using a reference time system. The reference time system is typically
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UTC.
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<p>
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Since the posix_time system does no internal time adjustment it
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can be used to represent both local times and UTC times. However,
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the user is currently left to handle conversions and time zone
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knowledge explicitly.
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<p>
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The library offers two different ways to perform UTC to local conversions.
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The first is using the time zone settings of the computer. This is
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a useful solution for converting a UTC time for a user machine. This
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approach depends on the ctime API and will provide incorrect results
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if the environment is set incorrectly.
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The other approach allows conversion from any zone to UTC and back
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independent of the settings of the time zone settings of the
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computer. The <a href="exp-local_utc_conversion.html">local utc conversion example</a>
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demonstrates both of these techniques.
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<p>
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<h2><a name="header">Header</a></h2>
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<pre>
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#include "boost/date_time/gregorian/gregorian.hpp" //include all types plus i/o
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or
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#include "boost/date_time/gregorian/gregorian_types.hpp" //no i/o just types
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</pre>
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<p>
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<h2><a name="classoverview">Class Overview</a></h2>
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<p>
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<table border=1 cellspacing=3 cellpadding=3>
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<tr><td><b>Class</b></td>
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<td><b>Description</b></td>
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<td><b>Example</b></td></tr>
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<tr><td>date_time::c_local_adjustor<ptime>::<font class="el">utc_to_local</font>(ptime)</td>
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<td>Calculate local machine time from a UTC time based on time zone settings and the C API.</td>
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<td>
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typedef boost::date_time::c_local_adjustor<ptime> local_adj;<br>
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ptime t10(date(2002,Jan,1), hours(7)); <br>
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ptime t11 = local_adj::utc_to_local(t10);<br>
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</td></tr>
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<tr><td>date_time::local_adjustor<ptime, utc_offset, dst_rules>::<font class="el">utc_to_local</font>(ptime)</td>
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<td>Calculate local machine time from a UTC time based daylight savings rules and utc offset</td>
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<td><a href="exp-local_utc_conversion.html">example</a>
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</td></tr>
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<tr><td>date_time::local_adjustor<ptime, utc_offset, dst_rules>::<font class="el">local_to_utc</font>(ptime)</td>
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<td>Calculate UTC time based on daylight savings rules and utc offset.</td>
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<td><a href="exp-local_utc_conversion.html">example</a>
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</td></tr>
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</table>
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<p>
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<hr>
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<address><small>
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<!-- hhmts start -->
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Last modified: Thu Sep 5 07:34:28 MST 2002
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<!-- hhmts end -->
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by <a href="mailto:jeff@crystalclearsoftware.com">Jeff Garland</a> © 2000-2002
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</small></address>
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</body>
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</html>
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