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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"../../../tools/boostbook/dtd/boostbook.dtd">
<!-- Copyright (c) 2001-2004 CrystalClear Software, Inc.
Subject to the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
-->
<section id="date_time.examples.local_utc_conversion">
<title>Local to UTC Conversion</title>
<para>
Demonstrate utc to local and local to utc calculations including dst.
</para>
<programlisting>
<![CDATA[
/* Demonstrate conversions between a local time and utc
* Output:
*
* UTC <--> New York while DST is NOT active (5 hours)
* 2001-Dec-31 19:00:00 in New York is 2002-Jan-01 00:00:00 UTC time
* 2002-Jan-01 00:00:00 UTC is 2001-Dec-31 19:00:00 New York time
*
* UTC <--> New York while DST is active (4 hours)
* 2002-May-31 20:00:00 in New York is 2002-Jun-01 00:00:00 UTC time
* 2002-Jun-01 00:00:00 UTC is 2002-May-31 20:00:00 New York time
*
* UTC <--> Arizona (7 hours)
* 2002-May-31 17:00:00 in Arizona is 2002-Jun-01 00:00:00 UTC time
*/
#include "boost/date_time/posix_time/posix_time.hpp"
#include "boost/date_time/local_time_adjustor.hpp"
#include "boost/date_time/c_local_time_adjustor.hpp"
#include <iostream>
int
main()
{
using namespace boost::posix_time;
using namespace boost::gregorian;
//This local adjustor depends on the machine TZ settings-- highly dangerous!
typedef boost::date_time::c_local_adjustor<ptime> local_adj;
ptime t10(date(2002,Jan,1), hours(7));
ptime t11 = local_adj::utc_to_local(t10);
std::cout << "UTC <--> Zone base on TZ setting" << std::endl;
std::cout << to_simple_string(t11) << " in your TZ is "
<< to_simple_string(t10) << " UTC time "
<< std::endl;
time_duration td = t11 - t10;
std::cout << "A difference of: "
<< to_simple_string(td) << std::endl;
//eastern timezone is utc-5
typedef boost::date_time::local_adjustor<ptime, -5, us_dst> us_eastern;
ptime t1(date(2001,Dec,31), hours(19)); //5 hours b/f midnight NY time
std::cout << "\nUTC <--> New York while DST is NOT active (5 hours)"
<< std::endl;
ptime t2 = us_eastern::local_to_utc(t1);
std::cout << to_simple_string(t1) << " in New York is "
<< to_simple_string(t2) << " UTC time "
<< std::endl;
ptime t3 = us_eastern::utc_to_local(t2);//back should be the same
std::cout << to_simple_string(t2) << " UTC is "
<< to_simple_string(t3) << " New York time "
<< "\n\n";
ptime t4(date(2002,May,31), hours(20)); //4 hours b/f midnight NY time
std::cout << "UTC <--> New York while DST is active (4 hours)" << std::endl;
ptime t5 = us_eastern::local_to_utc(t4);
std::cout << to_simple_string(t4) << " in New York is "
<< to_simple_string(t5) << " UTC time "
<< std::endl;
ptime t6 = us_eastern::utc_to_local(t5);//back should be the same
std::cout << to_simple_string(t5) << " UTC is "
<< to_simple_string(t6) << " New York time "
<< "\n" << std::endl;
//Arizona timezone is utc-7 with no dst
typedef boost::date_time::local_adjustor<ptime, -7, no_dst> us_arizona;
ptime t7(date(2002,May,31), hours(17));
std::cout << "UTC <--> Arizona (7 hours)" << std::endl;
ptime t8 = us_arizona::local_to_utc(t7);
std::cout << to_simple_string(t7) << " in Arizona is "
<< to_simple_string(t8) << " UTC time "
<< std::endl;
return 0;
}
]]>
</programlisting>
</section>
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