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  27 <a name="date_time.examples.general_usage_examples"></a>General Usage Examples</h2></div></div></div>
  28 <p>
  29     The following provides some sample usage of dates.
  30     See <a class="link" href="../gregorian.html" title="Gregorian">Date Programming</a>
  31     for more details.
  32
  33     </p>
  34 <pre class="programlisting"><span class="keyword">using namespace</span> boost::gregorian;
  35     date weekstart(<span class="number">2002</span>,Feb,<span class="number">1</span>);
  36     date weekend  = weekstart + weeks(<span class="number">1</span>);
  37     date d2 = d1 + days(<span class="number">5</span>);
  38     date today = day_clock::local_day();
  39     if (d2 &gt;= today) {} <span class="comment">//date comparison operators</span>
  40
  41     date_period thisWeek(d1,d2);
  42     <span class="keyword">if</span> (thisWeek.contains(today)) {}<span class="comment">//do something
  43
  44     //iterate and print the week</span>
  45     day_iterator itr(weekstart);
  46     <span class="keyword">while</span> (itr &lt;= weekend) {
  47      std::cout &lt;&lt; (*itr) &lt;&lt; std::endl;
  48      ++itr;
  49     }
  50     <span class="comment">//input streaming</span>
  51     std::stringstream ss(<span class="string">"2004-Jan-1"</span>);
  52     ss &gt;&gt; d3;
  53
  54     <span class="comment">//date generator functions</span>
  55     date d5 = next_weekday(d4, Sunday); <span class="comment">//calculate Sunday following d4
  56
  57     //US labor day is first Monday in Sept</span>
  58         <span class="keyword">typedef</span> nth_day_of_the_week_in_month nth_dow;
  59     nth_dow labor_day(nth_dow::first,Monday, Sep);
  60     <span class="comment">//calculate a specific date for 2004 from functor</span>
  61     date d6 = labor_day.get_date(<span class="number">2004</span>);
  62     </pre>
  63 <p>
  64
  65       The following provides some example code using times.
  66       See <a class="link" href="../posix_time.html" title="Posix Time">Time Programming</a>
  67       for more details.
  68
  69     </p>
  70 <pre class="programlisting"><span class="keyword">using namespace</span> boost::posix_time;
  71     date d(<span class="number">2002</span>,Feb,<span class="number">1</span>); <span class="comment">//an arbitrary date</span>
  72     ptime t1(d, hours(<span class="number">5</span>)+nanosec(<span class="number">100</span>)); <span class="comment">//date + time of day offset</span>
  73     ptime t2 = t1 - minutes(<span class="number">4</span>)+seconds(<span class="number">2</span>);
  74     ptime now = second_clock::local_time(); <span class="comment">//use the clock</span>
  75     date today = now.date(); <span class="comment">//Get the date part out of the time</span>
  76     date tomorrow = today + date_duration(<span class="number">1</span>);
  77     ptime tomorrow_start(tomorrow); <span class="comment">//midnight
  78
  79     //input streaming</span>
  80     std::stringstream ss(<span class="string">"2004-Jan-1 05:21:33.20"</span>);
  81     ss &gt;&gt; t2;
  82
  83     <span class="comment">//starting at current time iterator adds by one hour</span>
  84     time_iterator titr(now,hours(<span class="number">1</span>));
  85     <span class="keyword">for</span> (; titr &lt; tomorrow_start; ++titr) {
  86      std::cout &lt;&lt; (*titr) &lt;&lt; std::endl;
  87     }
  88     </pre>
  89 <p>
  90   </p>
  91 <p>
  92       The following provides some example code using times.
  93       See <a class="link" href="../local_time.html" title="Local Time">Local Time Programming</a>
  94       for more details.
  95
  96     </p>
  97 <pre class="programlisting">
  98     <span class="keyword">using namespace</span> boost::local_time;
  99     <span class="comment">//setup some timezones for creating and adjusting times
 100     //first time zone uses the time zone file for regional timezone definitions</span>
 101     tz_database tz_db;
 102     tz_db.load_from_file(<span class="string">"date_time_zonespec.csv"</span>);
 103     time_zone_ptr nyc_tz = tz_db.time_zone_from_region(<span class="string">"America/New_York"</span>);
 104     <span class="comment">//This timezone uses a posix time zone string definition to create a time zone</span>
 105     time_zone_ptr phx_tz(new posix_time_zone(<span class="string">"MST-07:00:00"</span>));
 106
 107     <span class="comment">//local departure time in phoenix is 11 pm on April 2 2005
 108     // Note that New York changes to daylight savings on Apr 3 at 2 am)</span>
 109     local_date_time phx_departure(date(<span class="number">2005</span>, Apr, <span class="number">2</span>), hours(<span class="number">23</span>), phx_tz,
 110                                   local_date_time::NOT_DATE_TIME_ON_ERROR);
 111
 112     time_duration flight_length = hours(<span class="number">4</span>) + minutes(<span class="number">30</span>);
 113     local_date_time phx_arrival = phx_departure + flight_length;
 114     <span class="comment">//convert the phx time to a nyz time</span>
 115     local_date_time nyc_arrival = phx_arrival.local_time_in(nyc_tz);
 116
 117     <span class="comment">//2005-Apr-03 06:30:00 EDT</span>
 118     std::cout &lt;&lt; nyc_arrival &lt;&lt; std::endl;
 119     </pre>
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