date_time/xmldoc/usage_examples.xml

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<section id="date_time.examples.general_usage_examples">
  <title>General Usage Examples</title>

  <para>
    The following provides some sample usage of dates.
    See <link linkend="date_time.gregorian">Date Programming</link> 
    for more details.

    <programlisting><emphasis role="keyword">using namespace</emphasis> boost::gregorian;
    date weekstart(<emphasis role="number">2002</emphasis>,Feb,<emphasis role="number">1</emphasis>);
    date weekend  = weekstart + weeks(<emphasis role="number">1</emphasis>);
    date d2 = d1 + days(<emphasis role="number">5</emphasis>);
    date today = day_clock::local_day();
    if (d2 &gt;= today) {} <emphasis role="comment">//date comparison operators</emphasis> 

    date_period thisWeek(d1,d2);
    <emphasis role="keyword">if</emphasis> (thisWeek.contains(today)) {}<emphasis role="comment">//do something 

    //iterate and print the week</emphasis>
    day_iterator itr(weekstart);
    <emphasis role="keyword">while</emphasis> (itr &lt;= weekend) {
     std::cout &lt;&lt; (*itr) &lt;&lt; std::endl;
     ++itr;
    }  
    <emphasis role="comment">//input streaming</emphasis> 
    std::stringstream ss(<emphasis role="string">"2004-Jan-1"</emphasis>);
    ss &gt;&gt; d3;

    <emphasis role="comment">//date generator functions</emphasis> 
    date d5 = next_weekday(d4, Sunday); <emphasis role="comment">//calculate Sunday following d4

    //US labor day is first Monday in Sept</emphasis> 
	<emphasis role="keyword">typedef</emphasis> nth_day_of_the_week_in_month nth_dow;
    nth_dow labor_day(nth_dow::first,Monday, Sep); 
    <emphasis role="comment">//calculate a specific date for 2004 from functor</emphasis> 
    date d6 = labor_day.get_date(<emphasis role="number">2004</emphasis>); 
    </programlisting>    

      The following provides some example code using times.
      See <link linkend="date_time.posix_time">Time Programming</link> 
      for more details.

    <programlisting><emphasis role="keyword">using namespace</emphasis> boost::posix_time; 
    date d(<emphasis role="number">2002</emphasis>,Feb,<emphasis role="number">1</emphasis>); <emphasis role="comment">//an arbitrary date</emphasis> 
    ptime t1(d, hours(<emphasis role="number">5</emphasis>)+nanosec(<emphasis role="number">100</emphasis>)); <emphasis role="comment">//date + time of day offset</emphasis> 
    ptime t2 = t1 - minutes(<emphasis role="number">4</emphasis>)+seconds(<emphasis role="number">2</emphasis>);
    ptime now = second_clock::local_time(); <emphasis role="comment">//use the clock</emphasis> 
    date today = now.date(); <emphasis role="comment">//Get the date part out of the time</emphasis> 
    date tomorrow = today + date_duration(<emphasis role="number">1</emphasis>);
    ptime tomorrow_start(tomorrow); <emphasis role="comment">//midnight 

    //input streaming</emphasis> 
    std::stringstream ss(<emphasis role="string">"2004-Jan-1 05:21:33.20"</emphasis>);
    ss &gt;&gt; t2;

    <emphasis role="comment">//starting at current time iterator adds by one hour</emphasis>
    time_iterator titr(now,hours(<emphasis role="number">1</emphasis>)); 
    <emphasis role="keyword">for</emphasis> (; titr &lt; tomorrow_start; ++titr) {
     std::cout &lt;&lt; (*titr) &lt;&lt; std::endl;
    }
    </programlisting>    
  </para>

  <para>
      The following provides some example code using times.
      See <link linkend="date_time.local_time">Local Time Programming</link> 
      for more details.

    <programlisting>
    <emphasis role="keyword">using namespace</emphasis> boost::local_time; 
    <emphasis role="comment">//setup some timezones for creating and adjusting times
    //first time zone uses the time zone file for regional timezone definitions</emphasis>
    tz_database tz_db;
    tz_db.load_from_file(<emphasis role="string">"date_time_zonespec.csv"</emphasis>);
    time_zone_ptr nyc_tz = tz_db.time_zone_from_region(<emphasis role="string">"America/New_York"</emphasis>);
    <emphasis role="comment">//This timezone uses a posix time zone string definition to create a time zone</emphasis>
    time_zone_ptr phx_tz(new posix_time_zone(<emphasis role="string">"MST-07:00:00"</emphasis>));

    <emphasis role="comment">//local departure time in phoenix is 11 pm on April 2 2005 
    // Note that New York changes to daylight savings on Apr 3 at 2 am)</emphasis>
    local_date_time phx_departure(date(<emphasis role="number">2005</emphasis>, Apr, <emphasis role="number">2</emphasis>), hours(<emphasis role="number">23</emphasis>), phx_tz, 
                                  local_date_time::NOT_DATE_TIME_ON_ERROR);

    time_duration flight_length = hours(<emphasis role="number">4</emphasis>) + minutes(<emphasis role="number">30</emphasis>);
    local_date_time phx_arrival = phx_departure + flight_length;
    <emphasis role="comment">//convert the phx time to a nyz time</emphasis>
    local_date_time nyc_arrival = phx_arrival.local_time_in(nyc_tz);

    <emphasis role="comment">//2005-Apr-03 06:30:00 EDT</emphasis>
    std::cout &lt;&lt; nyc_arrival &lt;&lt; std::endl;
    </programlisting>    
  </para>
  
</section>