...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Various parsing and output of strings.
/* 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 <iostream> #include <string> 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 << to_simple_string(d) << 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 << to_iso_extended_string(d1) << 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 << wd.as_long_string() << " " << ymd.month.as_long_string() << " " << ymd.day << ", " << ymd.year << std::endl; //Let's send in month 25 by accident and create an exception std::string bad_date("20012509"); //2001-??-09 std::cout << "An expected exception is next: " << 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 << "oh oh, you shouldn't reach this line: " << to_iso_string(wont_construct) << std::endl; } catch(std::exception& e) { std::cout << " Exception: " << e.what() << std::endl; } return 0; }
Calculate the number of days you have been living using durations and dates.
/* 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.
*/
#include "boost/date_time/gregorian/gregorian.hpp"
#include <iostream>
int
main()
{
using namespace boost::gregorian;
std::string s;
std::cout << "Enter birth day YYYY-MM-DD (eg: 2002-02-01): ";
std::cin >> s;
try {
date birthday(from_simple_string(s));
date today = day_clock::local_day();
days days_alive = today - birthday;
days one_day(1);
if (days_alive == one_day) {
std::cout << "Born yesterday, very funny" << std::endl;
}
else if (days_alive < days(0)) {
std::cout << "Not born yet, hmm: " << days_alive.days()
<< " days" <<std::endl;
}
else {
std::cout << "Days alive: " << days_alive.days() << std::endl;
}
}
catch(...) {
std::cout << "Bad date entered: " << s << std::endl;
}
return 0;
}
Calculate the number of days till new years
/* 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 <iostream> #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 << "Days since Jan 1: " << days_since_year_start.days() << std::endl; days days_until_year_start = new_years_day.get_date(today.year()+1) - today; std::cout << "Days until next Jan 1: " << days_until_year_start.days() << std::endl; return 0; };
Example that gets a month and a year from the user and finds the last day of each remaining month of that year.
/* 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 <iostream> 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 << " Enter Year(ex: 2002): "; std::cin >> y; year = greg_year(y); std::cout << " Enter Month(1..12): "; std::cin >> m; month = greg_month(m); } catch(bad_year by) { std::cout << "Invalid Year Entered: " << by.what() << '\n' << "Using minimum values for month and year." << std::endl; } catch(bad_month bm) { std::cout << "Invalid Month Entered" << bm.what() << '\n' << "Using minimum value for month. " << 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 < start_of_next_year){ std::cout << to_simple_string(d.end_of_month()) << std::endl; d += months(1); } return 0; }
The boost::date_time library provides the ability to create customized locale facets. Date ordering, language, seperators, and abbreviations can be customized.
/* 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 <iostream> #include <algorithm> /* 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(&de_short_month_names[0], &de_short_month_names[11], std::back_inserter(short_months)); std::copy(&de_long_month_names[0], &de_long_month_names[11], std::back_inserter(long_months)); std::copy(&de_short_weekday_names[0], &de_short_weekday_names[6], std::back_inserter(short_weekdays)); std::copy(&de_long_weekday_names[0], &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->short_month_names(short_months); german_facet->long_month_names(long_months); german_facet->short_weekday_names(short_weekdays); german_facet->long_weekday_names(long_weekdays); // output the date in German using short month names german_facet->format("%d.%m.%Y"); std::cout << d1 << std::endl; //01.10.2002 german_facet->month_format("%B"); std::cout << m << std::endl; //Oktober german_facet->weekday_format("%A"); std::cout << wd << 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->format("%m/%d/%Y"); std::cout << d1 << std::endl; // 10/01/2002 // English names, ISO 8601 order (year-month-day), '-' separator us_facet->format("%Y-%b-%d"); std::cout << d1 << std::endl; // 2002-Oct-01 return 0; }
Calculates if a date is in an 'irregular' collection of periods using period calculation functions.
/* 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 --> 20020216/20020217 20020223/20020224 */ #include "boost/date_time/gregorian/gregorian.hpp" #include <set> #include <algorithm> #include <iostream> typedef std::set<boost::gregorian::date_period> 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<date_period_set> 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 << "Number Excluded Periods: " << ps.size() << 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 << to_iso_string(*i) << std::endl; //if date is in exclusion period then print it if (i->contains(d)) { std::cout << "In Exclusion Period: " << to_iso_string(d) << " --> " << to_iso_string(*i) << std::endl; } } return 0; }
This is an example of using functors to define a holiday schedule
/* 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 <algorithm> #include <functional> #include <vector> #include <iostream> #include <set> void print_date(boost::gregorian::date d) { using namespace boost::gregorian; #if defined(BOOST_DATE_TIME_NO_LOCALE) std::cout << to_simple_string(d) << " [" << d.day_of_week() << "]\n"; #else std::cout << d << " [" << d.day_of_week() << "]\n"; #endif } int main() { std::cout << "Enter Year: "; int year; std::cin >> year; using namespace boost::gregorian; //define a collection of holidays fixed by month and day std::vector<year_based_generator*> 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<date> date_set; date_set all_holidays; for(std::vector<year_based_generator*>::iterator it = holidays.begin(); it != holidays.end(); ++it) { all_holidays.insert((*it)->get_date(year)); } //print the holidays to the screen std::for_each(all_holidays.begin(), all_holidays.end(), print_date); std::cout << "Number Holidays: " << all_holidays.size() << std::endl; return 0; }
Simple utility to print out days of the month with the days of a month. Demontstrates date iteration (date_time::date_itr).
/* 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 <iostream> int main() { std::cout << "Enter Year: "; int year, month; std::cin >> year; std::cout << "Enter Month(1..12): "; std::cin >> 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 <= endOfMonth; ++ditr) { #if defined(BOOST_DATE_TIME_NO_LOCALE) std::cout << to_simple_string(*ditr) << " [" #else std::cout << *ditr << " [" #endif << ditr->day_of_week() << "]" << std::endl; } } catch(std::exception& e) { std::cout << "Error bad date, check your entry: \n" << " Details: " << e.what() << std::endl; } return 0; }
Adding a month to a day without the use of iterators.
/* 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 <iostream> 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 << "Today is: " << to_simple_string(d) << ".\n" << "One month from today will be: " << to_simple_string(d2) << std::endl; return 0; }
Various types of calculations with times and time durations.
/* 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 <iostream> 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 << to_simple_string(t2) << " - " << to_simple_string(t1) << " = " << to_simple_string(td) << std::endl; return 0; }
Demonstrate time iteration, clock retrieval, and simple calculation.
/* 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 <iostream> 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 < tommorrow_start; ++titr) { std::cout << to_simple_string(*titr) << std::endl; } time_duration remaining = tommorrow_start - now; std::cout << "Time left till midnight: " << to_simple_string(remaining) << std::endl; return 0; }
Demonstrate utc to local and local to utc calculations including dst.
/* 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; }
Demonstrate some simple uses of time periods.
/* 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 <iostream> 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 << to_simple_string(dp) << " contains " << to_simple_string(t) << 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 << to_simple_string(dp) << " intersected with\n" << to_simple_string(part_of_day) << " is \n" << to_simple_string(result) << std::endl; } return 0; }
Example usage of custom_time_zone as well as posix_time_zone.
/* A simple example for using a custom_time_zone and a posix_time_zone. */ #include "boost/date_time/local_time/local_time.hpp" #include <iostream> 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<dst_calc_rule> 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<dst_calc_rule> 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 << "The first zone is in daylight savings from:\n " << nyc_1->dst_local_start_time(2004) << " through " << nyc_1->dst_local_end_time(2004) << std::endl; std::cout << "The second zone is in daylight savings from:\n " << nyc_2->dst_local_start_time(2004) << " through " << nyc_2->dst_local_end_time(2004) << std::endl; std::cout << "The third zone (no daylight savings):\n " << phx_1->std_zone_abbrev() << " and " << phx_1->base_utc_offset() << std::endl; std::cout << "The fourth zone (no daylight savings):\n " << phx_2->std_zone_abbrev() << " and " << phx_2->base_utc_offset() << std::endl; return 0; }
Example of creating various Daylight Savings Calc Rule objects.
/* 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 <iostream> 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; }
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).
#include "boost/date_time/local_time/local_time.hpp"
#include <iostream>
/* 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).
*
*
*/
int main()
{
using namespace boost::gregorian;
using namespace boost::local_time;
using namespace boost::posix_time;
//setup some timezones for creating and adjusting local times
//This user editable file can be found in libs/date_time/data.
tz_database tz_db;
tz_db.load_from_file("date_time_zonespec.csv");
time_zone_ptr nyc_tz = tz_db.time_zone_from_region("America/New_York");
//Use a
time_zone_ptr phx_tz(new posix_time_zone("MST-07:00:00"));
//local departure time in phoenix is 11 pm on april 2 2005
// (ny changes to dst on apr 3 at 2 am)
local_date_time phx_departure(date(2005, Apr, 2), hours(23),
phx_tz,
local_date_time::NOT_DATE_TIME_ON_ERROR);
time_duration flight_length = hours(4) + minutes(30);
local_date_time phx_arrival = phx_departure + flight_length;
local_date_time nyc_arrival = phx_arrival.local_time_in(nyc_tz);
std::cout << "departure phx time: " << phx_departure << std::endl;
std::cout << "arrival phx time: " << phx_arrival << std::endl;
std::cout << "arrival nyc time: " << nyc_arrival << std::endl;
}
Example of calculating seconds elapsed since epoch (1970-Jan-1) using local_date_time.
/* 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 <iostream> 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 << "Error with time zone data file: " << dna.what() << std::endl; exit(EXIT_FAILURE); }catch(bad_field_count bfc) { std::cerr << "Error with time zone data file: " << bfc.what() << 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 << nyc_time << std::endl; ptime time_t_epoch(date(1970,1,1)); std::cout << time_t_epoch << 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 << "Seconds diff: " << diff.total_seconds() << std::endl; }