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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="date_time.examples"></a>Examples</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="examples.html#date_time.examples.dates_as_strings">Dates as Strings</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.days_alive">Days Alive</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.days_between_new_year">Days Between New Years</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.end_of_month_day">Last Day of the Months</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.localization">Localization Demonstration</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.date_period_calc">Date Period Calculations</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.print_holidays">Print Holidays</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.print_month">Print Month</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.month_add">Month Adding</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.time_math">Time Math</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.print_hours">Print Hours</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.local_utc_conversion">Local to UTC Conversion</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.time_periods">Time Periods</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.simple_time_zone">Simple Time Zones</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.calc_rules">Daylight Savings Calc Rules</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.flight">Flight Time Example</a></span></dt>
<dt><span class="section"><a href="examples.html#date_time.examples.seconds_since_epoch">Seconds Since Epoch</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.dates_as_strings"></a>Dates as Strings</h3></div></div></div>
<p>  
    Various parsing and output of strings.
  </p>
<pre class="programlisting">
    

  /* The following is a simple example that shows conversion of dates 
   * to and from a std::string.
   * 
   * Expected output:
   * 2001-Oct-09
   * 2001-10-09
   * Tuesday October 9, 2001
   * An expected exception is next: 
   * Exception: Month number is out of range 1..12
   */

  #include "boost/date_time/gregorian/gregorian.hpp"
  #include &lt;iostream&gt;
  #include &lt;string&gt;

  int
  main() 
  {

    using namespace boost::gregorian;

    try {
      // The following date is in ISO 8601 extended format (CCYY-MM-DD)
      std::string s("2001-10-9"); //2001-October-09
      date d(from_simple_string(s));
      std::cout &lt;&lt; to_simple_string(d) &lt;&lt; std::endl;
      
      //Read ISO Standard(CCYYMMDD) and output ISO Extended
      std::string ud("20011009"); //2001-Oct-09
      date d1(from_undelimited_string(ud));
      std::cout &lt;&lt; to_iso_extended_string(d1) &lt;&lt; std::endl;
      
      //Output the parts of the date - Tuesday October 9, 2001
      date::ymd_type ymd = d1.year_month_day();
      greg_weekday wd = d1.day_of_week();
      std::cout &lt;&lt; wd.as_long_string() &lt;&lt; " "
                &lt;&lt; ymd.month.as_long_string() &lt;&lt; " "
                &lt;&lt; ymd.day &lt;&lt; ", " &lt;&lt; ymd.year
                &lt;&lt; std::endl;

      //Let's send in month 25 by accident and create an exception
      std::string bad_date("20012509"); //2001-??-09
      std::cout &lt;&lt; "An expected exception is next: " &lt;&lt; std::endl;
      date wont_construct(from_undelimited_string(bad_date));
      //use wont_construct so compiler doesn't complain, but you wont get here!
      std::cout &lt;&lt; "oh oh, you shouldn't reach this line: " 
                &lt;&lt; to_iso_string(wont_construct) &lt;&lt; std::endl;
    }
    catch(std::exception&amp; e) {
      std::cout &lt;&lt; "  Exception: " &lt;&lt;  e.what() &lt;&lt; std::endl;
    }


    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.days_alive"></a>Days Alive</h3></div></div></div>
<p> 
    Calculate the number of days you have been living using durations and dates.
  </p>
<pre class="programlisting">
<code class="literal">
<span class="comment">/* Short example that calculates the number of days since user was born.
 * Demonstrates comparisons of durations, use of the day_clock,
 * and parsing a date from a string.
 */</span><span class="preprocessor">

#include</span><span class="string"> "boost/date_time/gregorian/gregorian.hpp"</span><span class="preprocessor">
#include</span><span class="special"> &lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span><span class="keyword">

int</span><span class="identifier">
main</span><span class="special">()</span><span class="special"> 
{</span><span class="keyword">
  
  using</span><span class="keyword"> namespace</span><span class="identifier"> boost</span><span class="special">::</span><span class="identifier">gregorian</span><span class="special">;</span><span class="identifier">
  std</span><span class="special">::</span><span class="identifier">string</span><span class="identifier"> s</span><span class="special">;</span><span class="identifier">
  std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "Enter birth day YYYY-MM-DD (eg: 2002-02-01): "</span><span class="special">;</span><span class="identifier">
  std</span><span class="special">::</span><span class="identifier">cin</span><span class="special"> &gt;&gt;</span><span class="identifier"> s</span><span class="special">;</span><span class="keyword">
  try</span><span class="special"> {</span><span class="identifier">
    date</span><span class="identifier"> birthday</span><span class="special">(</span><span class="identifier">from_simple_string</span><span class="special">(</span><span class="identifier">s</span><span class="special">));</span><span class="identifier">
    date</span><span class="identifier"> today</span><span class="special"> =</span><span class="identifier"> day_clock</span><span class="special">::</span><span class="identifier">local_day</span><span class="special">();</span><span class="identifier">
    days</span><span class="identifier"> days_alive</span><span class="special"> =</span><span class="identifier"> today</span><span class="special"> -</span><span class="identifier"> birthday</span><span class="special">;</span><span class="identifier">
    days</span><span class="identifier"> one_day</span><span class="special">(</span><span class="number">1</span><span class="special">);</span><span class="keyword">
    if</span><span class="special"> (</span><span class="identifier">days_alive</span><span class="special"> ==</span><span class="identifier"> one_day</span><span class="special">)</span><span class="special"> {</span><span class="identifier">
      std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "Born yesterday, very funny"</span><span class="special"> &lt;&lt;</span><span class="identifier"> std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span><span class="special">
    }</span><span class="keyword">
    else</span><span class="keyword"> if</span><span class="special"> (</span><span class="identifier">days_alive</span><span class="special"> &lt;</span><span class="identifier"> days</span><span class="special">(</span><span class="number">0</span><span class="special">))</span><span class="special"> {</span><span class="identifier">
      std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "Not born yet, hmm: "</span><span class="special"> &lt;&lt;</span><span class="identifier"> days_alive</span><span class="special">.</span><span class="identifier">days</span><span class="special">()</span><span class="special"> 
                &lt;&lt;</span><span class="string"> " days"</span><span class="special"> &lt;&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span><span class="special">
    }</span><span class="keyword">
    else</span><span class="special"> {</span><span class="identifier">
      std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "Days alive: "</span><span class="special"> &lt;&lt;</span><span class="identifier"> days_alive</span><span class="special">.</span><span class="identifier">days</span><span class="special">()</span><span class="special"> &lt;&lt;</span><span class="identifier"> std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span><span class="special">
    }</span><span class="special">

  }</span><span class="keyword">
  catch</span><span class="special">(...)</span><span class="special"> {</span><span class="identifier">
    std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "Bad date entered: "</span><span class="special"> &lt;&lt;</span><span class="identifier"> s</span><span class="special"> &lt;&lt;</span><span class="identifier"> std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span><span class="special">
  }</span><span class="keyword">
  return</span><span class="number"> 0</span><span class="special">;</span><span class="special">
}</span>
</code>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.days_between_new_year"></a>Days Between New Years</h3></div></div></div>
<p>  
    Calculate the number of days till new years
  </p>
<pre class="programlisting">
    
  /* Provides a simple example of using a date_generator, and simple
   * mathematical operatorations, to calculate the days since 
   * New Years day of this year, and days until next New Years day.
   *
   * Expected results:
   * Adding together both durations will produce 366 (365 in a leap year).
   */
  #include &lt;iostream&gt;
  #include "boost/date_time/gregorian/gregorian.hpp"

  int
  main() 
  {
    
    using namespace boost::gregorian;

    date today = day_clock::local_day();
    partial_date new_years_day(1,Jan);
    //Subtract two dates to get a duration
    days days_since_year_start = today - new_years_day.get_date(today.year());
    std::cout &lt;&lt; "Days since Jan 1: " &lt;&lt; days_since_year_start.days() 
              &lt;&lt; std::endl;
    
    days days_until_year_start = new_years_day.get_date(today.year()+1) - today;
    std::cout &lt;&lt; "Days until next Jan 1: " &lt;&lt; days_until_year_start.days() 
              &lt;&lt; std::endl;
    return 0;
  };

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.end_of_month_day"></a>Last Day of the Months</h3></div></div></div>
<p>
    Example that gets a month and a year from the user and finds the last day of each remaining month of that year.
  </p>
<pre class="programlisting">
    
  /* Simple program that finds the last day of the given month, 
   * then displays the last day of every month left in the given year.
   */

  #include "boost/date_time/gregorian/gregorian.hpp"
  #include &lt;iostream&gt;

  int
  main()
  {
    using namespace boost::gregorian;
    
    greg_year year(1400);
    greg_month month(1);

    // get a month and a year from the user
    try {
      int y, m;
      std::cout &lt;&lt; "   Enter Year(ex: 2002): ";
      std::cin &gt;&gt; y;
      year = greg_year(y);
      std::cout &lt;&lt; "   Enter Month(1..12): ";
      std::cin &gt;&gt; m;
      month = greg_month(m);
    }
    catch(bad_year by) {
      std::cout &lt;&lt; "Invalid Year Entered: " &lt;&lt; by.what() &lt;&lt; '\n'
        &lt;&lt; "Using minimum values for month and year." &lt;&lt; std::endl;
    }
    catch(bad_month bm) {
      std::cout &lt;&lt; "Invalid Month Entered" &lt;&lt; bm.what() &lt;&lt; '\n'
        &lt;&lt; "Using minimum value for month. " &lt;&lt; std::endl;
    }
    
    date start_of_next_year(year+1, Jan, 1);
    date d(year, month, 1);
    
    // add another month to d until we enter the next year.
    while (d &lt; start_of_next_year){
      std::cout &lt;&lt; to_simple_string(d.end_of_month()) &lt;&lt; std::endl;
      d += months(1);
    }

    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.localization"></a>Localization Demonstration</h3></div></div></div>
<p>
    The boost::date_time library provides the ability to create customized locale facets. Date ordering, language, seperators, and abbreviations can be customized.
  </p>
<pre class="programlisting">
    
  /* The following shows the creation of a facet for the output of 
   * dates in German (please forgive me for any errors in my German --
   * I'm not a native speaker).
   */

  #include "boost/date_time/gregorian/gregorian.hpp"
  #include &lt;iostream&gt;
  #include &lt;algorithm&gt;

  /* Define a series of char arrays for short and long name strings 
   * to be associated with German date output (US names will be 
   * retrieved from the locale). */
  const char* const de_short_month_names[] = 
  {
    "Jan", "Feb", "Mar", "Apr", "Mai", "Jun",
    "Jul", "Aug", "Sep", "Okt", "Nov", "Dez", "NAM" 
  };
  const char* const de_long_month_names[] =
  {
    "Januar", "Februar", "Marz", "April", "Mai",
    "Juni", "Juli", "August", "September", "Oktober",
    "November", "Dezember", "NichtDerMonat"
  };
  const char* const de_long_weekday_names[] = 
  {
    "Sonntag", "Montag", "Dienstag", "Mittwoch",
    "Donnerstag", "Freitag", "Samstag"
  };
  const char* const de_short_weekday_names[] =
  {
    "Son", "Mon", "Die","Mit", "Don", "Fre", "Sam"
  };


  int main() 
  {
    using namespace boost::gregorian;
   
    // create some gregorian objects to output
    date d1(2002, Oct, 1);
    greg_month m = d1.month();
    greg_weekday wd = d1.day_of_week();
    
    // create a facet and a locale for German dates
    date_facet* german_facet = new date_facet();
    std::cout.imbue(std::locale(std::locale::classic(), german_facet));

    // create the German name collections
    date_facet::input_collection_type short_months, long_months, 
                                      short_weekdays, long_weekdays;
    std::copy(&amp;de_short_month_names[0], &amp;de_short_month_names[11],
              std::back_inserter(short_months));
    std::copy(&amp;de_long_month_names[0], &amp;de_long_month_names[11],
              std::back_inserter(long_months));
    std::copy(&amp;de_short_weekday_names[0], &amp;de_short_weekday_names[6],
              std::back_inserter(short_weekdays));
    std::copy(&amp;de_long_weekday_names[0], &amp;de_long_weekday_names[6],
              std::back_inserter(long_weekdays));

    // replace the default names with ours
    // NOTE: date_generators and special_values were not replaced as 
    // they are not used in this example
    german_facet-&gt;short_month_names(short_months);
    german_facet-&gt;long_month_names(long_months);
    german_facet-&gt;short_weekday_names(short_weekdays);
    german_facet-&gt;long_weekday_names(long_weekdays);
    
    // output the date in German using short month names
    german_facet-&gt;format("%d.%m.%Y");
    std::cout &lt;&lt; d1 &lt;&lt; std::endl; //01.10.2002
    
    german_facet-&gt;month_format("%B");
    std::cout &lt;&lt; m &lt;&lt; std::endl; //Oktober
    
    german_facet-&gt;weekday_format("%A");
    std::cout &lt;&lt; wd &lt;&lt; std::endl; //Dienstag


    // Output the same gregorian objects using US names
    date_facet* us_facet = new date_facet();
    std::cout.imbue(std::locale(std::locale::classic(), us_facet)); 

    us_facet-&gt;format("%m/%d/%Y");
    std::cout &lt;&lt; d1 &lt;&lt; std::endl; //  10/01/2002
    
    // English names, iso order (year-month-day), '-' separator
    us_facet-&gt;format("%Y-%b-%d");
    std::cout &lt;&lt; d1 &lt;&lt; std::endl; //  2002-Oct-01
    
    return 0;

  }
    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.date_period_calc"></a>Date Period Calculations</h3></div></div></div>
<p>  
    Calculates if a date is in an 'irregular' collection of periods using period calculation functions.
  </p>
<pre class="programlisting">
    
  /*
  This example demonstrates a simple use of periods for the calculation
  of date information.

  The example calculates if a given date is a weekend or holiday
  given an exclusion set.  That is, each weekend or holiday is
  entered into the set as a time interval.  Then if a given date
  is contained within any of the intervals it is considered to
  be within the exclusion set and hence is a offtime.

  Output:
  Number Excluded Periods: 5
  20020202/20020203
  20020209/20020210
  20020212/20020212
  20020216/20020217
  In Exclusion Period: 20020216 --&gt; 20020216/20020217
  20020223/20020224

  */


  #include "boost/date_time/gregorian/gregorian.hpp"
  #include &lt;set&gt;
  #include &lt;algorithm&gt;
  #include &lt;iostream&gt;

  typedef std::set&lt;boost::gregorian::date_period&gt; date_period_set;

  //Simple population of the exclusion set
  date_period_set
  generateExclusion()
  {
    using namespace boost::gregorian;
    date_period periods_array[] = 
      { date_period(date(2002,Feb,2), date(2002,Feb,4)),//weekend of 2nd-3rd
        date_period(date(2002,Feb,9), date(2002,Feb,11)),
        date_period(date(2002,Feb,16), date(2002,Feb,18)),
        date_period(date(2002,Feb,23), date(2002,Feb,25)),
        date_period(date(2002,Feb,12), date(2002,Feb,13))//a random holiday 2-12
      };
    const int num_periods = sizeof(periods_array)/sizeof(date_period);

    date_period_set ps;
    //insert the periods in the set
    std::insert_iterator&lt;date_period_set&gt; itr(ps, ps.begin());
    std::copy(periods_array, periods_array+num_periods, itr );
    return ps;
    
  }


  int main() 
  {
    using namespace boost::gregorian;
    
    date_period_set ps = generateExclusion();
    std::cout &lt;&lt; "Number Excluded Periods: "  &lt;&lt; ps.size() &lt;&lt; std::endl;

    date d(2002,Feb,16);
    date_period_set::const_iterator i = ps.begin();
    //print the periods, check for containment
    for (;i != ps.end(); i++) {
      std::cout &lt;&lt; to_iso_string(*i) &lt;&lt; std::endl;
      //if date is in exclusion period then print it
      if (i-&gt;contains(d)) {
        std::cout &lt;&lt; "In Exclusion Period: "
            &lt;&lt; to_iso_string(d) &lt;&lt; " --&gt; " &lt;&lt; to_iso_string(*i)
            &lt;&lt; std::endl;
      }
    }

    return 0;  

  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.print_holidays"></a>Print Holidays</h3></div></div></div>
<p>  
    This is an example of using functors to define a holiday schedule
  </p>
<pre class="programlisting">
    

  /* Generate a set of dates using a collection of date generators
   * Output looks like:
   * Enter Year: 2002
   * 2002-Jan-01 [Tue]
   * 2002-Jan-21 [Mon]
   * 2002-Feb-12 [Tue]
   * 2002-Jul-04 [Thu]
   * 2002-Sep-02 [Mon]
   * 2002-Nov-28 [Thu]
   * 2002-Dec-25 [Wed]
   * Number Holidays: 7
   */

  #include "boost/date_time/gregorian/gregorian.hpp"
  #include &lt;algorithm&gt;
  #include &lt;functional&gt;
  #include &lt;vector&gt;
  #include &lt;iostream&gt;
  #include &lt;set&gt;

  void
  print_date(boost::gregorian::date d) 
  {
    using namespace boost::gregorian;
  #if defined(BOOST_DATE_TIME_NO_LOCALE)
    std::cout &lt;&lt; to_simple_string(d) &lt;&lt; " [" &lt;&lt; d.day_of_week() &lt;&lt; "]\n";
  #else
    std::cout &lt;&lt; d &lt;&lt; " [" &lt;&lt; d.day_of_week() &lt;&lt; "]\n";
  #endif
  }


  int
  main() {

    std::cout &lt;&lt; "Enter Year: ";
    int year;
    std::cin &gt;&gt; year;

    using namespace boost::gregorian;

    //define a collection of holidays fixed by month and day
    std::vector&lt;year_based_generator*&gt; holidays;
    holidays.push_back(new partial_date(1,Jan)); //Western New Year
    holidays.push_back(new partial_date(4,Jul)); //US Independence Day
    holidays.push_back(new partial_date(25, Dec));//Christmas day


    //define a shorthand for the nth_day_of_the_week_in_month function object
    typedef nth_day_of_the_week_in_month nth_dow;
    
    //US labor day
    holidays.push_back(new nth_dow(nth_dow::first,  Monday,   Sep)); 
    //MLK Day
    holidays.push_back(new nth_dow(nth_dow::third,  Monday,   Jan)); 
    //Pres day
    holidays.push_back(new nth_dow(nth_dow::second, Tuesday,  Feb)); 
    //Thanksgiving
    holidays.push_back(new nth_dow(nth_dow::fourth, Thursday, Nov)); 

    typedef std::set&lt;date&gt; date_set;
    date_set all_holidays;
    
    for(std::vector&lt;year_based_generator*&gt;::iterator it = holidays.begin();
        it != holidays.end(); ++it)
    {
      all_holidays.insert((*it)-&gt;get_date(year));
    }

    //print the holidays to the screen
    std::for_each(all_holidays.begin(), all_holidays.end(), print_date);
    std::cout &lt;&lt; "Number Holidays: " &lt;&lt; all_holidays.size() &lt;&lt; std::endl;

    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.print_month"></a>Print Month</h3></div></div></div>
<p>  
    Simple utility to print out days of the month with the days of a month. Demontstrates date iteration (date_time::date_itr).
  </p>
<pre class="programlisting">
    
  /* This example prints all the dates in a month. It demonstrates
   * the use of iterators as well as functions of the gregorian_calendar
   * 
   * Output:
   * Enter Year: 2002
   * Enter Month(1..12): 2
   * 2002-Feb-01 [Fri]
   * 2002-Feb-02 [Sat]
   * 2002-Feb-03 [Sun]
   * 2002-Feb-04 [Mon]
   * 2002-Feb-05 [Tue]
   * 2002-Feb-06 [Wed]
   * 2002-Feb-07 [Thu]
   */

  #include "boost/date_time/gregorian/gregorian.hpp"
  #include &lt;iostream&gt;

  int
  main()
  {
    std::cout &lt;&lt; "Enter Year: ";
    int year, month;
    std::cin &gt;&gt; year;
    std::cout &lt;&lt; "Enter Month(1..12): ";
    std::cin &gt;&gt; month;

    using namespace boost::gregorian;
    try {
      //Use the calendar to get the last day of the month
      int eom_day = gregorian_calendar::end_of_month_day(year,month);
      date endOfMonth(year,month,eom_day);

      //construct an iterator starting with firt day of the month
      day_iterator ditr(date(year,month,1));
      //loop thru the days and print each one
      for (; ditr &lt;= endOfMonth; ++ditr) {
  #if defined(BOOST_DATE_TIME_NO_LOCALE) 
        std::cout &lt;&lt; to_simple_string(*ditr) &lt;&lt; " ["
  #else
        std::cout &lt;&lt; *ditr &lt;&lt; " ["
  #endif
                  &lt;&lt; ditr-&gt;day_of_week() &lt;&lt; "]"
                  &lt;&lt; std::endl; 
      }
    }
    catch(std::exception&amp; e) {

      std::cout &lt;&lt; "Error bad date, check your entry: \n"
                &lt;&lt; "  Details: " &lt;&lt; e.what() &lt;&lt; std::endl;
    }
    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.month_add"></a>Month Adding</h3></div></div></div>
<p> 
    Adding a month to a day without the use of iterators.
  </p>
<pre class="programlisting">
    
  /* Simple program that uses the gregorian calendar to progress by exactly
   * one month, irregardless of how many days are in that month.
   *
   * This method can be used as an alternative to iterators
   */

  #include "boost/date_time/gregorian/gregorian.hpp"
  #include &lt;iostream&gt;

  int
  main()
  {

    using namespace boost::gregorian;

    date d = day_clock::local_day();
    add_month mf(1);
    date d2 = d + mf.get_offset(d);
    std::cout &lt;&lt; "Today is: " &lt;&lt; to_simple_string(d) &lt;&lt; ".\n"
      &lt;&lt; "One month from today will be: " &lt;&lt; to_simple_string(d2) 
      &lt;&lt; std::endl;

    return 0;
  }
    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.time_math"></a>Time Math</h3></div></div></div>
<p> 
    Various types of calculations with times and time durations.  
  </p>
<pre class="programlisting">
    
  /* Some simple examples of constructing and calculating with times
   * Output:
   * 2002-Feb-01 00:00:00 - 2002-Feb-01 05:04:02.001000000 = -5:04:02.001000000
   */

  #include "boost/date_time/posix_time/posix_time.hpp"
  #include &lt;iostream&gt;

  int
  main() 
  {
    using namespace boost::posix_time;
    using namespace boost::gregorian;

    date d(2002,Feb,1); //an arbitrary date
    //construct a time by adding up some durations durations
    ptime t1(d, hours(5)+minutes(4)+seconds(2)+millisec(1));
    //construct a new time by subtracting some times
    ptime t2 = t1 - hours(5)- minutes(4)- seconds(2)- millisec(1);
    //construct a duration by taking the difference between times
    time_duration td = t2 - t1;
      
    std::cout &lt;&lt; to_simple_string(t2) &lt;&lt; " - " 
              &lt;&lt; to_simple_string(t1) &lt;&lt; " = "
              &lt;&lt; to_simple_string(td) &lt;&lt; std::endl;
    
    return 0;
  }
    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.print_hours"></a>Print Hours</h3></div></div></div>
<p>
    Demonstrate time iteration, clock retrieval, and simple calculation. 
  </p>
<pre class="programlisting">
    
  /* Print the remaining hours of the day
   * Uses the clock to get the local time 
   * Use an iterator to iterate over the remaining hours
   * Retrieve the date part from a time
   *
   * Expected Output something like:
   *
   * 2002-Mar-08 16:30:59
   * 2002-Mar-08 17:30:59
   * 2002-Mar-08 18:30:59
   * 2002-Mar-08 19:30:59
   * 2002-Mar-08 20:30:59
   * 2002-Mar-08 21:30:59
   * 2002-Mar-08 22:30:59
   * 2002-Mar-08 23:30:59
   * Time left till midnight: 07:29:01
   */

  #include "boost/date_time/posix_time/posix_time.hpp"
  #include &lt;iostream&gt;

  int
  main() 
  {
    using namespace boost::posix_time;
    using namespace boost::gregorian;

    //get the current time from the clock -- one second resolution
    ptime now = second_clock::local_time();
    //Get the date part out of the time
    date today = now.date();
    date tommorrow = today + days(1);
    ptime tommorrow_start(tommorrow); //midnight 

    //iterator adds by one hour
    time_iterator titr(now,hours(1)); 
    for (; titr &lt; tommorrow_start; ++titr) {
      std::cout &lt;&lt; to_simple_string(*titr) &lt;&lt; std::endl;
    }
    
    time_duration remaining = tommorrow_start - now;
    std::cout &lt;&lt; "Time left till midnight: " 
              &lt;&lt; to_simple_string(remaining) &lt;&lt; std::endl;
    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.local_utc_conversion"></a>Local to UTC Conversion</h3></div></div></div>
<p>
    Demonstrate utc to local and local to utc calculations including dst.
  </p>
<pre class="programlisting">
    

  /* Demonstrate conversions between a local time and utc
   * Output:
   * 
   * UTC &lt;--&gt; 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 &lt;--&gt; 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 &lt;--&gt; 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 &lt;iostream&gt;

  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&lt;ptime&gt; local_adj;
    ptime t10(date(2002,Jan,1), hours(7)); 
    ptime t11 = local_adj::utc_to_local(t10);
    std::cout &lt;&lt; "UTC &lt;--&gt; Zone base on TZ setting" &lt;&lt; std::endl;
    std::cout &lt;&lt; to_simple_string(t11) &lt;&lt; " in your TZ is " 
              &lt;&lt; to_simple_string(t10) &lt;&lt; " UTC time "
              &lt;&lt; std::endl;
    time_duration td = t11 - t10;
    std::cout &lt;&lt; "A difference of: " 
              &lt;&lt; to_simple_string(td) &lt;&lt; std::endl;


    //eastern timezone is utc-5
    typedef boost::date_time::local_adjustor&lt;ptime, -5, us_dst&gt; us_eastern;

    ptime t1(date(2001,Dec,31), hours(19)); //5 hours b/f midnight NY time

    std::cout &lt;&lt; "\nUTC &lt;--&gt; New York while DST is NOT active (5 hours)" 
              &lt;&lt; std::endl;
    ptime t2 =  us_eastern::local_to_utc(t1);
    std::cout &lt;&lt; to_simple_string(t1) &lt;&lt; " in New York is " 
              &lt;&lt; to_simple_string(t2) &lt;&lt; " UTC time "
              &lt;&lt; std::endl;

    ptime t3 = us_eastern::utc_to_local(t2);//back should be the same
    std::cout &lt;&lt; to_simple_string(t2) &lt;&lt; " UTC is " 
              &lt;&lt; to_simple_string(t3) &lt;&lt; " New York time "
              &lt;&lt; "\n\n";

    ptime t4(date(2002,May,31), hours(20)); //4 hours b/f midnight NY time
    std::cout &lt;&lt; "UTC &lt;--&gt; New York while DST is active (4 hours)" &lt;&lt; std::endl;
    ptime t5 = us_eastern::local_to_utc(t4);
    std::cout &lt;&lt; to_simple_string(t4) &lt;&lt; " in New York is " 
              &lt;&lt; to_simple_string(t5) &lt;&lt; " UTC time "
              &lt;&lt; std::endl;

    ptime t6 = us_eastern::utc_to_local(t5);//back should be the same
    std::cout &lt;&lt; to_simple_string(t5) &lt;&lt; " UTC is " 
              &lt;&lt; to_simple_string(t6) &lt;&lt; " New York time "
              &lt;&lt; "\n" &lt;&lt; std::endl;

      
    //Arizona timezone is utc-7 with no dst
    typedef boost::date_time::local_adjustor&lt;ptime, -7, no_dst&gt; us_arizona;

    ptime t7(date(2002,May,31), hours(17)); 
    std::cout &lt;&lt; "UTC &lt;--&gt; Arizona (7 hours)" &lt;&lt; std::endl;
    ptime t8 = us_arizona::local_to_utc(t7);
    std::cout &lt;&lt; to_simple_string(t7) &lt;&lt; " in Arizona is " 
              &lt;&lt; to_simple_string(t8) &lt;&lt; " UTC time "
              &lt;&lt; std::endl;

    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.time_periods"></a>Time Periods</h3></div></div></div>
<p>
    Demonstrate some simple uses of time periods. 
  </p>
<pre class="programlisting">
    

  /* Some simple examples of constructing and calculating with times
   * Returns:
   * [2002-Feb-01 00:00:00/2002-Feb-01 23:59:59.999999999] 
   * contains 2002-Feb-01 03:00:05
   * [2002-Feb-01 00:00:00/2002-Feb-01 23:59:59.999999999] 
   * intersected with
   * [2002-Feb-01 00:00:00/2002-Feb-01 03:00:04.999999999] 
   * is 
   * [2002-Feb-01 00:00:00/2002-Feb-01 03:00:04.999999999]
   */

  #include "boost/date_time/posix_time/posix_time.hpp"
  #include &lt;iostream&gt;

  using namespace boost::posix_time;
  using namespace boost::gregorian;

  //Create a simple period class to contain all the times in a day
  class day_period : public time_period
  {
  public:
    day_period(date d) : time_period(ptime(d),//midnight
                                     ptime(d,hours(24)))
    {}

  };

  int
  main() 
  {

    date d(2002,Feb,1); //an arbitrary date
    //a period that represents a day  
    day_period dp(d);
    ptime t(d, hours(3)+seconds(5)); //an arbitray time on that day
    if (dp.contains(t)) {
      std::cout &lt;&lt; to_simple_string(dp) &lt;&lt; " contains "
                &lt;&lt; to_simple_string(t)  &lt;&lt; std::endl;
    }
    //a period that represents part of the day
    time_period part_of_day(ptime(d, hours(0)), t);
    //intersect the 2 periods and print the results
    if (part_of_day.intersects(dp)) {
      time_period result = part_of_day.intersection(dp);
      std::cout &lt;&lt; to_simple_string(dp) &lt;&lt; " intersected with\n"
                &lt;&lt; to_simple_string(part_of_day) &lt;&lt; " is \n"
                &lt;&lt; to_simple_string(result) &lt;&lt; std::endl;
    }
      
    
    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.simple_time_zone"></a>Simple Time Zones</h3></div></div></div>
<p> 
    Example usage of custom_time_zone as well as posix_time_zone.
  </p>
<pre class="programlisting">
    
  /* A simple example for using a custom_time_zone and a posix_time_zone.
   */

  #include "boost/date_time/local_time/local_time.hpp"
  #include &lt;iostream&gt;

  int
  main() 
  {
    using namespace boost;
    using namespace local_time;
    using namespace gregorian;
    using posix_time::time_duration;

    /***** custom_time_zone *****/
    
    // create the dependent objects for a custom_time_zone
    time_zone_names tzn("Eastern Standard Time", "EST",
                        "Eastern Daylight Time", "EDT");
    time_duration utc_offset(-5,0,0);
    dst_adjustment_offsets adj_offsets(time_duration(1,0,0), 
                                       time_duration(2,0,0), 
                                       time_duration(2,0,0));
    // rules for this zone are:
    // start on first Sunday of April at 2 am
    // end on last Sunday of October at 2 am
    // so we use a first_last_dst_rule
    first_day_of_the_week_in_month start_rule(Sunday, Apr);
    last_day_of_the_week_in_month    end_rule(Sunday, Oct);
    shared_ptr&lt;dst_calc_rule&gt; nyc_rules(new first_last_dst_rule(start_rule, 
                                                                end_rule));
    // create more dependent objects for a non-dst custom_time_zone
    time_zone_names tzn2("Mountain Standard Time", "MST",
                         "", ""); // no dst means empty dst strings
    time_duration utc_offset2(-7,0,0);
    dst_adjustment_offsets adj_offsets2(time_duration(0,0,0), 
                                        time_duration(0,0,0), 
                                        time_duration(0,0,0));
    // no dst means we need a null pointer to the rules
    shared_ptr&lt;dst_calc_rule&gt; phx_rules;

    // create the custom_time_zones
    time_zone_ptr nyc_1(new custom_time_zone(tzn, utc_offset, 
                                             adj_offsets, nyc_rules));
    time_zone_ptr phx_1(new custom_time_zone(tzn2, utc_offset2, 
                                             adj_offsets2, phx_rules));

    /***** posix_time_zone *****/

    // create posix_time_zones that are the duplicates of the 
    // custom_time_zones created above. See posix_time_zone documentation 
    // for details on full zone names.
    std::string nyc_string, phx_string;
    nyc_string = "EST-05:00:00EDT+01:00:00,M4.1.0/02:00:00,M10.5.0/02:00:00";
    // nyc_string = "EST-05EDT,M4.1.0,M10.5.0"; // shorter when defaults used
    phx_string = "MST-07"; // no-dst
    time_zone_ptr nyc_2(new posix_time_zone(nyc_string));
    time_zone_ptr phx_2(new posix_time_zone(phx_string));
   

    /***** show the sets are equal *****/

    std::cout &lt;&lt; "The first zone is in daylight savings from:\n " 
      &lt;&lt; nyc_1-&gt;dst_local_start_time(2004) &lt;&lt; " through "
      &lt;&lt; nyc_1-&gt;dst_local_end_time(2004) &lt;&lt; std::endl;

    std::cout &lt;&lt; "The second zone is in daylight savings from:\n " 
      &lt;&lt; nyc_2-&gt;dst_local_start_time(2004) &lt;&lt; " through "
      &lt;&lt; nyc_2-&gt;dst_local_end_time(2004) &lt;&lt; std::endl;

    std::cout &lt;&lt; "The third zone (no daylight savings):\n " 
      &lt;&lt; phx_1-&gt;std_zone_abbrev() &lt;&lt; " and "
      &lt;&lt; phx_1-&gt;base_utc_offset() &lt;&lt; std::endl;

    std::cout &lt;&lt; "The fourth zone (no daylight savings):\n " 
      &lt;&lt; phx_2-&gt;std_zone_abbrev() &lt;&lt; " and "
      &lt;&lt; phx_2-&gt;base_utc_offset() &lt;&lt; std::endl;

    return 0;
  }
    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.calc_rules"></a>Daylight Savings Calc Rules</h3></div></div></div>
<p> 
    Example of creating various Daylight Savings Calc Rule objects.
  </p>
<pre class="programlisting">
    
  /* A simple example for creating various dst_calc_rule instances
   */

  #include "boost/date_time/gregorian/gregorian.hpp"
  #include "boost/date_time/local_time/local_time.hpp"
  #include &lt;iostream&gt;

  int
  main() 
  {
    using namespace boost;
    using namespace local_time;
    using namespace gregorian;

    /***** create the necessary date_generator objects *****/
    // starting generators
    first_day_of_the_week_in_month fd_start(Sunday, May);
    last_day_of_the_week_in_month ld_start(Sunday, May);
    nth_day_of_the_week_in_month nkd_start(nth_day_of_the_week_in_month::third, 
                                           Sunday, May);
    partial_date pd_start(1, May);
    // ending generators
    first_day_of_the_week_in_month fd_end(Sunday, Oct);
    last_day_of_the_week_in_month ld_end(Sunday, Oct);
    nth_day_of_the_week_in_month nkd_end(nth_day_of_the_week_in_month::third, 
                                         Sunday, Oct);
    partial_date pd_end(31, Oct);

    /***** create the various dst_calc_rule objects *****/
    dst_calc_rule_ptr pdr(new partial_date_dst_rule(pd_start, pd_end));
    dst_calc_rule_ptr flr(new first_last_dst_rule(fd_start, ld_end));
    dst_calc_rule_ptr llr(new last_last_dst_rule(ld_start, ld_end));
    dst_calc_rule_ptr nlr(new nth_last_dst_rule(nkd_start, ld_end));
    dst_calc_rule_ptr ndr(new nth_day_of_the_week_in_month_dst_rule(nkd_start, 
                                                                    nkd_end));

    return 0;
  }

    
  </pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.flight"></a>Flight Time Example</h3></div></div></div>
<p>This example shows a program that calculates the arrival time of a plane that flys from Phoenix to New York.  During the flight New York shifts into daylight savings time (Phoenix doesn't because Arizona doesn't use dst).</p>
<pre class="programlisting">
<code class="literal">
<span class="preprocessor">#include</span><span class="string"> "boost/date_time/local_time/local_time.hpp"</span><span class="preprocessor">
#include</span><span class="special"> &lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span><span class="comment">

/* This example shows a program that calculates the arrival time of a plane
 * that flys from Phoenix to New York.  During the flight New York shifts
 * into daylight savings time (Phoenix doesn't because Arizona doesn't use
 * dst).  
 *
 * 
 */</span><span class="keyword">

int</span><span class="identifier"> main</span><span class="special">()</span><span class="special">
{</span><span class="keyword">
  using</span><span class="keyword"> namespace</span><span class="identifier"> boost</span><span class="special">::</span><span class="identifier">gregorian</span><span class="special">;</span><span class="keyword"> 
  using</span><span class="keyword"> namespace</span><span class="identifier"> boost</span><span class="special">::</span><span class="identifier">local_time</span><span class="special">;</span><span class="keyword">
  using</span><span class="keyword"> namespace</span><span class="identifier"> boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">;</span><span class="comment">


  //setup some timezones for creating and adjusting local times
  //This user editable file can be found in libs/date_time/data.
</span><span class="identifier">  tz_database</span><span class="identifier"> tz_db</span><span class="special">;</span><span class="identifier">
  tz_db</span><span class="special">.</span><span class="identifier">load_from_file</span><span class="special">(</span><span class="string">"date_time_zonespec.csv"</span><span class="special">);</span><span class="identifier">
  time_zone_ptr</span><span class="identifier"> nyc_tz</span><span class="special"> =</span><span class="identifier"> tz_db</span><span class="special">.</span><span class="identifier">time_zone_from_region</span><span class="special">(</span><span class="string">"America/New_York"</span><span class="special">);</span><span class="comment">
  //Use a 
</span><span class="identifier">  time_zone_ptr</span><span class="identifier"> phx_tz</span><span class="special">(</span><span class="keyword">new</span><span class="identifier"> posix_time_zone</span><span class="special">(</span><span class="string">"MST-07:00:00"</span><span class="special">));</span><span class="comment">

  //local departure time in phoenix is 11 pm on april 2 2005 
  // (ny changes to dst on apr 3 at 2 am)
</span><span class="identifier">  local_date_time</span><span class="identifier"> phx_departure</span><span class="special">(</span><span class="identifier">date</span><span class="special">(</span><span class="number">2005</span><span class="special">,</span><span class="identifier"> Apr</span><span class="special">,</span><span class="number"> 2</span><span class="special">),</span><span class="identifier"> hours</span><span class="special">(</span><span class="number">23</span><span class="special">),</span><span class="identifier"> 
                                phx_tz</span><span class="special">,</span><span class="identifier"> 
                                local_date_time</span><span class="special">::</span><span class="identifier">NOT_DATE_TIME_ON_ERROR</span><span class="special">);</span><span class="identifier">

  time_duration</span><span class="identifier"> flight_length</span><span class="special"> =</span><span class="identifier"> hours</span><span class="special">(</span><span class="number">4</span><span class="special">)</span><span class="special"> +</span><span class="identifier"> minutes</span><span class="special">(</span><span class="number">30</span><span class="special">);</span><span class="identifier">
  local_date_time</span><span class="identifier"> phx_arrival</span><span class="special"> =</span><span class="identifier"> phx_departure</span><span class="special"> +</span><span class="identifier"> flight_length</span><span class="special">;</span><span class="identifier">
  local_date_time</span><span class="identifier"> nyc_arrival</span><span class="special"> =</span><span class="identifier"> phx_arrival</span><span class="special">.</span><span class="identifier">local_time_in</span><span class="special">(</span><span class="identifier">nyc_tz</span><span class="special">);</span><span class="identifier">

  std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "departure phx time: "</span><span class="special"> &lt;&lt;</span><span class="identifier"> phx_departure</span><span class="special"> &lt;&lt;</span><span class="identifier"> std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span><span class="identifier">
  std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "arrival phx time:   "</span><span class="special"> &lt;&lt;</span><span class="identifier"> phx_arrival</span><span class="special"> &lt;&lt;</span><span class="identifier"> std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span><span class="identifier">
  std</span><span class="special">::</span><span class="identifier">cout</span><span class="special"> &lt;&lt;</span><span class="string"> "arrival nyc time:   "</span><span class="special"> &lt;&lt;</span><span class="identifier"> nyc_arrival</span><span class="special"> &lt;&lt;</span><span class="identifier"> std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span><span class="special">

}</span>
</code>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="date_time.examples.seconds_since_epoch"></a>Seconds Since Epoch</h3></div></div></div>
<p> 
    Example of calculating seconds elapsed since epoch (1970-Jan-1) using local_date_time.
  </p>
<pre class="programlisting">
    
  /* This example demonstrates the use of the time zone database and 
   * local time to calculate the number of seconds since the UTC
   * time_t epoch 1970-01-01 00:00:00.  Note that the selected timezone
   * could be any timezone supported in the time zone database file which
   * can be modified and updated as needed by the user.
   *
   * To solve this problem the following steps are required:
   * 1) Get a timezone from the tz database for the local time
   * 2) Construct a local time using the timezone
   * 3) Construct a posix_time::ptime for the time_t epoch time
   * 4) Convert the local_time to utc and subtract the epoch time
   * 
   */

  #include "boost/date_time/local_time/local_time.hpp"
  #include &lt;iostream&gt;

  int main()
  {
    using namespace boost::gregorian; 
    using namespace boost::local_time;
    using namespace boost::posix_time;
    
    tz_database tz_db;
    try {
      tz_db.load_from_file("../data/date_time_zonespec.csv");
    }catch(data_not_accessible dna) {
      std::cerr &lt;&lt; "Error with time zone data file: " &lt;&lt; dna.what() &lt;&lt; std::endl;
      exit(EXIT_FAILURE);
    }catch(bad_field_count bfc) {
      std::cerr &lt;&lt; "Error with time zone data file: " &lt;&lt; bfc.what() &lt;&lt; std::endl;
      exit(EXIT_FAILURE);
    }

    time_zone_ptr nyc_tz = tz_db.time_zone_from_region("America/New_York");
    date in_date(2004,10,04);
    time_duration td(12,14,32);
    // construct with local time value
    // create not-a-date-time if invalid (eg: in dst transition)
    local_date_time nyc_time(in_date, 
                             td, 
                             nyc_tz, 
                             local_date_time::NOT_DATE_TIME_ON_ERROR);

    std::cout &lt;&lt; nyc_time &lt;&lt; std::endl;

    ptime time_t_epoch(date(1970,1,1)); 
    std::cout &lt;&lt; time_t_epoch &lt;&lt; std::endl;

    // first convert nyc_time to utc via the utc_time() 
    // call and subtract the ptime.
    time_duration diff = nyc_time.utc_time() - time_t_epoch;

    //Expected 1096906472
    std::cout &lt;&lt; "Seconds diff: " &lt;&lt; diff.total_seconds() &lt;&lt; std::endl;

  }
    
  </pre>
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