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Created Boost datetime Examples Translated (markdown)
HowardHinnant
561
Boost-datetime-Examples-Translated.md
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561
Boost-datetime-Examples-Translated.md
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This page shows how the boost datetime examples shown here:
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http://www.boost.org/doc/libs/1_59_0/doc/html/date_time/examples.html#date_time.examples.time_math
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look if ported to this library.
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##Contents
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- [Dates as Strings](#Dates_as_Strings)
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- [Days Alive](#Days_Alive)
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- [Days Between New Years](#Days_Between_New_Years)
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- [Last Day of the Months](#Last_Day_of_the_Months)
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- [Localization Demonstration](#Localization_Demonstration)
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- [Date Period Calculations](#Date_Period_Calculations)
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- [Print Holidays](#Print_Holidays)
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- [Print Month](#Print_Month)
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- [Month Adding](#Month_Adding)
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- [Time Math](#Time_Math)
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- [Print Hours](#Print_Hours)
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- [Local to UTC Conversion](#Local_to_UTC_Conversion)
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- [Time Periods](#Time_Periods)
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- [Simple Time Zones](#Simple_Time_Zones)
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- [Daylight Savings Calc Rules](#Daylight_Savings_Calc_Rules)
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- [Flight Time Example](#Flight_Time_Example)
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- [Seconds Since Epoch](#Seconds_Since_Epoch)
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***
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<a name="Dates_as_Strings"></a>
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###Dates as String
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#include "date.h"
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#include <cassert>
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#include <iostream>
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#include <sstream>
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#include <stdexcept>
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int
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main()
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{
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using namespace date;
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using namespace std;
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try
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{
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// The following date is in ISO 8601 extended format (CCYY-MM-DD)
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string s("2001-10-9"); // 2001-October-09
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istringstream in(s);
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int y, m, day;
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char dash;
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in >> y >> dash >> m >> dash >> day;
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auto d = year(y)/m/day;
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assert(d.ok());
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cout << d.year() << '-' << d.month() << '-' << d.day() << '\n'; // 2001-Oct-09
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// Read ISO Standard(CCYYMMDD) and output ISO Extended
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string ud("20011009"); // 2001-Oct-09
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auto d1 = year(stoi(ud.substr(0, 4)))/stoi(ud.substr(4, 2))/stoi(ud.substr(6, 2));
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assert(d1.ok());
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cout << d1 << '\n'; // 2001-10-09
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// Output the parts of the date - Tuesday October 9, 2001
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auto wd = weekday{d1};
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cout << wd << ' ' << d1.month() << ' ' << static_cast<unsigned>(d1.day())
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<< ", " << d1.year() << '\n'; // Tue Oct 9, 2001
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// Let's send in month 25 by accident and create an exception
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string bad_date("20012509"); // 2001-??-09
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cout << "An expected exception is next:\n";
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auto d2 = year(stoi(bad_date.substr(0,4)))/stoi(bad_date.substr(4,2))/stoi(bad_date.substr(6,2));
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if (!d2.ok())
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{
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ostringstream msg;
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msg << "Invalid date: " << d2;
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throw runtime_error(msg.str());
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}
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cout << "oh oh, you shouldn't reach this line:\n";
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}
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catch (const exception& e)
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{
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cout << "Exception: " << e.what() << '\n'; // Exception: Invalid date: 2001-25-09
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}
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}
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<a name="Days_Alive"></a>
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###Days Alive
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#include "date.h"
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#include "tz.h"
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#include <iostream>
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#include <sstream>
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int
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main()
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{
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std::string s;
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std::cout << "Enter birth day YYYY-MM-DD (eg: 2002-02-01): ";
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std::cin >> s;
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try
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{
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using namespace std::chrono;
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using namespace date;
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std::istringstream in(s);
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in.exceptions(std::ios::failbit);
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int y, m, day;
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char dash;
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in >> y >> dash >> m >> dash >> day;
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auto d = year(y)/m/day;
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if (!d.ok())
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throw std::exception{};
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auto birthday = day_point(d);
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auto today = floor<days>(current_zone()->to_local(system_clock::now()).first);
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auto days_alive = today - birthday;
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if (days_alive == days{1})
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std::cout << "Born yesterday, very funny\n";
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else if (days_alive < days{0})
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std::cout << "Not born yet, hmm: " << days_alive.count()
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<< " days\n";
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else
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std::cout << "Days alive: " << days_alive.count() << '\n';
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}
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catch (...)
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{
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std::cout << "Bad date entered: " << s << '\n';
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}
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}
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<a name="Days_Between_New_Years"></a>
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###Days Between New Years
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#include "date.h"
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#include "tz.h"
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#include <iostream>
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int
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main()
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{
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using namespace std::chrono;
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using namespace date;
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auto today = floor<days>(current_zone()->to_local(system_clock::now()).first);
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auto current_year = year_month_day{today}.year();
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auto days_since_year_start = today - day_point(current_year/jan/1);
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std::cout << "Days since Jan 1: " << days_since_year_start.count() << '\n';
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auto days_until_year_start = day_point((current_year + years{1})/jan/1) - today;
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std::cout << "Days until next Jan 1: " << days_until_year_start.count() << '\n';
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}
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<a name="Last_Day_of_the_Months"></a>
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###Last Day of the Months
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#include "date.h"
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#include <cassert>
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#include <iostream>
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int
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main()
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{
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using namespace date;
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int yi, mi;
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std::cout << " Enter Year(ex: 2002): ";
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std::cin >> yi;
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auto y = year(yi);
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assert(y.ok());
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std::cout << " Enter Month(1..12): ";
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std::cin >> mi;
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auto m = month(mi);
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assert(m.ok());
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auto start_of_next_year = (y + years{1})/jan/1;
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auto d = y/m/1;
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for (auto d = y/m/1; d < start_of_next_year; d += months{1})
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std::cout << year_month_day{d.year()/d.month()/last} << '\n';
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}
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<a name="Localization_Demonstration"></a>
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###Localization Demonstration
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#include "date.h"
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#include <iomanip>
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#include <iostream>
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// Define a series of char arrays for short and long name strings
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// to be associated with German date output (US names will be
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// retrieved from the locale).
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const char* const de_long_month_names[] =
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{
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"Januar", "Februar", "Marz", "April", "Mai",
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"Juni", "Juli", "August", "September", "Oktober",
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"November", "Dezember", "NichtDerMonat"
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};
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const char* const de_long_weekday_names[] =
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{
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"Sonntag", "Montag", "Dienstag", "Mittwoch",
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"Donnerstag", "Freitag", "Samstag"
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};
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int
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main()
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{
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using namespace date;
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// create some gregorian objects to output
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auto d1 = 2002_y/oct/1;
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auto m = d1.month();
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auto wd = weekday{d1};
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using namespace std;
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// output the date in German using short month names
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cout << d1.day() << '.' << setw(2) << static_cast<unsigned>(d1.month())
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<< '.' << d1.year() << '\n'; // 01.10.2002
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cout << de_long_month_names[static_cast<unsigned>(m)-1] << '\n'; // Oktober
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cout << de_long_weekday_names[static_cast<unsigned>(wd)] << '\n'; // Dienstag
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cout << static_cast<unsigned>(d1.month()) << '/' << d1.day()
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<< '/' << d1.year() << '\n'; // 10/01/2002
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cout << d1.year() << '-' << d1.month() << '-' << d1.day() << '\n'; // 2002-Oct-01
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}
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<a name="Date_Period_Calculations"></a>
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###Date Period Calculations
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#include "date.h"
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#include <iostream>
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#include <iterator>
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int
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main()
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{
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using namespace date;
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using date_period = std::pair<year_month_day, year_month_day>;
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constexpr date_period ps[] =
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{
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{feb/ 2/2002, feb/ 4/2002}, // weekend of 2nd-3rd
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{feb/ 9/2002, feb/11/2002},
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{feb/16/2002, feb/18/2002},
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{feb/23/2002, feb/25/2002},
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{feb/12/2002, feb/13/2002} // a random holiday 2-12
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};
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std::cout << "Number Excluded Periods: " << std::size(ps) << '\n';
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auto d = feb/16/2002;
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for (const auto& p : ps)
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{
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std::cout << p.first << " / " << p.second << '\n';
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if (p.first <= d && d < p.second)
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std::cout << "In Exclusion Period: "
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<< d << " --> "
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<< p.first << " / " << p.second << '\n';
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}
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}
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<a name="Print_Holidays"></a>
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###Print Holidays
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#include "date.h"
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#include <iostream>
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#include <vector>
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std::vector<date::day_point>
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generate_holidays(date::year y)
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{
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using namespace date;
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std::vector<day_point> holidays;
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holidays.push_back(y/jan/1); // Western New Year
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holidays.push_back(y/jul/4); // US Independence Day
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holidays.push_back(y/dec/25); // Christmas day
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holidays.push_back(y/sep/mon[1]); // US labor day
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holidays.push_back(y/jan/mon[3]); // MLK Day
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holidays.push_back(y/feb/tue[2]); // Pres day
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holidays.push_back(y/nov/thu[4]); // Thanksgiving
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std::sort(holidays.begin(), holidays.end());
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return holidays;
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}
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int
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main()
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{
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std::cout << "Enter Year: ";
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int y;
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std::cin >> y;
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using namespace date;
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//define a collection of holidays fixed by month and day
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auto holidays = generate_holidays(year{y});
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for (const auto& d : holidays)
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std::cout << d << " [" << weekday(d) << "]\n";
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std::cout << "Number Holidays: " << holidays.size() << '\n';
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}
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<a name="Print_Month"></a>
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###Print Month
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#include "date.h"
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#include <iostream>
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int
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main()
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{
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std::cout << "Enter Year: ";
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int yi, mi;
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std::cin >> yi;
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std::cout << "Enter Month(1..12): ";
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std::cin >> mi;
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try
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{
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using namespace date;
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auto ym = year(yi)/mi;
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if (!ym.ok())
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throw std::runtime_error("Bad year or month: "
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+ std::to_string(yi) + "/" + std::to_string(mi));
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auto wd = weekday{ym/1};
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auto endOfMonth = (ym/last).day();
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for (auto d = 1_d; d <= endOfMonth; d += days{1}, wd += days{1})
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std::cout << ym.year() << '-' << ym.month() << '-'
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<< d << " [" << wd << "]\n";
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}
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catch (const std::exception& e)
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{
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std::cerr << "Error bad date, check your entry: \n"
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<< " Details: " << e.what() << '\n';
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}
|
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}
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<a name="Month_Adding"></a>
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###Month Adding
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#include "date.h"
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#include "tz.h"
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#include <iostream>
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int
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main()
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{
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using namespace std::chrono;
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using namespace date;
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auto zone = current_zone();
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auto d = year_month_day{floor<days>(zone->to_local(system_clock::now()).first)};
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auto d2 = d + months{1};
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if (!d2.ok())
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d2 = d2.year()/d2.month()/last; // boost snaps to last
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std::cout << "Today is: " << d << ".\n"
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<< "One month from today will be: " << d2 << '\n';
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}
|
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|
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<a name="Time_Math"></a>
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###Time Math
|
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|
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#include "date.h"
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#include <iostream>
|
||||
|
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int
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||||
main()
|
||||
{
|
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using namespace std::chrono;
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using namespace date;
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auto d = day_point(2002_y/feb/1); // an arbitrary date;
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// construct a time by adding up some durations durations
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auto t1 = d + 5h + 4min + 2s + 1ms;
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// construct a new time by subtracting some times
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auto t2 = t1 - 5h - 4min - 2s - 1ms;
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// construct a duration by taking the difference between times
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auto td = t2 - t1;
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std::cout << t2 << " - " << t1 << " = " << make_time(td) << '\n';
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// 2002-02-01 00:00:00.000 - 2002-02-01 05:04:02.001 = -05:04:02.001
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}
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|
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<a name="Print_Hours"></a>
|
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###Print Hours
|
||||
|
||||
#include "date.h"
|
||||
#include "tz.h"
|
||||
#include <iostream>
|
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|
||||
int
|
||||
main()
|
||||
{
|
||||
using namespace std::chrono;
|
||||
using namespace date;
|
||||
// get the current time from the clock -- one second resolution
|
||||
auto now = floor<seconds>(current_zone()->to_local(system_clock::now()).first);
|
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// Get the date part out of the time
|
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auto today = floor<days>(now);
|
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auto tomorrow = today + days{1}; // midnight
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for (auto i = now; i < tomorrow; i += 1h)
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std::cout << i << '\n';
|
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auto remaining = tomorrow - now;
|
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std::cout << "Time left until midnight: " << make_time(remaining) << '\n';
|
||||
}
|
||||
|
||||
<a name="Local_to_UTC_Conversion"></a>
|
||||
###Local to UTC Conversion
|
||||
|
||||
#include "date.h"
|
||||
#include "tz.h"
|
||||
#include <iostream>
|
||||
|
||||
int
|
||||
main()
|
||||
{
|
||||
using namespace std::chrono;
|
||||
using namespace date;
|
||||
auto zone = current_zone();
|
||||
auto t10 = day_point(2002_y/jan/1) + 7h;
|
||||
auto t11 = zone->to_local(t10);
|
||||
std::cout << "UTC <--> Zone base on current setting\n";
|
||||
std::cout << t11.first << ' ' << t11.second << " is "
|
||||
<< t10 << " UTC time\n";
|
||||
auto td = t11.first - t10;
|
||||
std::cout << "A difference of: " << make_time(td) << '\n';
|
||||
|
||||
// eastern timezone is utc-5
|
||||
zone = locate_zone("America/New_York");
|
||||
auto t1 = day_point(2001_y/dec/31) + 19h + 0s; // 5 hours b/f midnight NY time
|
||||
std::cout << "\nUTC <--> New York while DST is NOT active (5 hours)\n";
|
||||
auto t2 = zone->to_sys(t1);
|
||||
std::cout << t1 << " in New York is " << t2 << " UTC time\n";
|
||||
|
||||
auto t3 = zone->to_local(t2).first; // back should be the same
|
||||
std::cout << t2 << " UTC is " << t3 << " New York time\n\n";
|
||||
|
||||
auto t4 = day_point(2002_y/may/31) + 20h + 0s; // 4 hours b/f midnight NY time
|
||||
std::cout << "UTC <--> New York while DST is active (4 hours)\n";
|
||||
auto t5 = zone->to_sys(t4);
|
||||
std::cout << t4 << " in New York is " << t5 << " UTC time\n";
|
||||
|
||||
auto t6 = zone->to_local(t5).first; // back should be the same
|
||||
std::cout << t5 << " UTC is " << t6 << " New York time\n\n";
|
||||
|
||||
// Arizona timezone is utc-7 with no dst
|
||||
zone = locate_zone("America/Phoenix");
|
||||
auto t7 = day_point(2002_y/may/31) + 17h + 0s;
|
||||
std::cout << "UTC <--> Arizona (7 hours)\n";
|
||||
auto t8 = zone->to_sys(t7);
|
||||
std::cout << t7 << " in Arizona is " << t8 << " UTC time\n";
|
||||
}
|
||||
|
||||
<a name="Time_Periods"></a>
|
||||
###Time Periods
|
||||
|
||||
#include "date.h"
|
||||
#include <iostream>
|
||||
|
||||
int
|
||||
main()
|
||||
{
|
||||
using namespace std::chrono;
|
||||
using namespace date;
|
||||
auto d = day_point(2002_y/feb/1); // an arbitrary date
|
||||
auto t = d + 3h + 5s; //an arbitray time on that day
|
||||
if (d <= t && t < d + days{1})
|
||||
std::cout << d << " contains " << t << '\n';
|
||||
// Time periods not part of this library but can be built from a pair of time_points.
|
||||
}
|
||||
|
||||
<a name="Simple_Time_Zones"></a>
|
||||
###Simple Time Zones
|
||||
|
||||
The boost example shows custom time zones. This library supports only the full history of the IANA timezone database. To achieve a custom timezone you would need to edit the IANA timezone database. For
|
||||
an example using the IANA timezone database see the [Local to UTC Conversion](#Local_to_UTC_Conversion) example.
|
||||
|
||||
<a name="Daylight_Savings_Calc_Rules"></a>
|
||||
###Daylight Savings Calc Rules
|
||||
|
||||
// This library does not support custom daylight savings rules. But it
|
||||
// does support the notion of partial dates and finding the nth (or last)
|
||||
// weekday of a month.
|
||||
|
||||
#include "date.h"
|
||||
|
||||
int
|
||||
main()
|
||||
{
|
||||
using namespace date;
|
||||
auto fd_start = sun[1]/may;
|
||||
auto ld_start = sun[last]/may;
|
||||
auto nkd_start = sun[3]/may;
|
||||
auto pd_start = may/1;
|
||||
auto fd_end = sun[1]/oct;
|
||||
auto ld_end = sun[last]/oct;
|
||||
auto nkd_end = sun[3]/oct;
|
||||
auto pd_end = oct/31;
|
||||
}
|
||||
|
||||
<a name="Flight_Time_Example"></a>
|
||||
###Flight Time Example
|
||||
|
||||
#include "date.h"
|
||||
#include "tz.h"
|
||||
#include <iostream>
|
||||
|
||||
int
|
||||
main()
|
||||
{
|
||||
using namespace std::chrono;
|
||||
using namespace date;
|
||||
|
||||
// set up some timezones for creating and adjusting local times
|
||||
auto nyc_tz = locate_zone("America/New_York");
|
||||
auto phx_tz = locate_zone("America/Phoenix");
|
||||
|
||||
// local departure time in phoenix is 11 pm on March 30 2005
|
||||
// (ny changes to dst on apr 3 at 2 am)
|
||||
auto phx_departure = day_point(2005_y/mar/30) + 23h + 0min;
|
||||
auto utc_departure = phx_tz->to_sys(phx_departure);
|
||||
|
||||
auto flight_length = 4h + 30min;
|
||||
auto utc_arrival = utc_departure + flight_length;
|
||||
|
||||
auto phx_arrival = phx_tz->to_local(utc_arrival);
|
||||
auto nyc_arrival = nyc_tz->to_local(utc_arrival);
|
||||
|
||||
std::cout << "departure phx time: " << phx_departure << '\n';
|
||||
std::cout << "arrival phx time: " << floor<minutes>(phx_arrival.first)
|
||||
<< ' ' << phx_arrival.second << '\n';
|
||||
std::cout << "arrival nyc time: " << floor<minutes>(nyc_arrival.first)
|
||||
<< ' ' << nyc_arrival.second << '\n';
|
||||
}
|
||||
|
||||
// Output:
|
||||
//
|
||||
// departure phx time: 2005-03-30 23:00
|
||||
// arrival phx time: 2005-03-31 03:30 MST
|
||||
// arrival nyc time: 2005-03-31 05:30 EST
|
||||
//
|
||||
// Note that boost states a nyc_arrival time of 2005-Mar-31 06:30:00 EDT
|
||||
// because boost uses the current US daylightsavings rules as opposed to
|
||||
// those that were in effect in 2005. This library varies its DST rules with the date.
|
||||
|
||||
<a name="Seconds_Since_Epoch"></a>
|
||||
###Seconds Since Epoch
|
||||
|
||||
#include "date.h"
|
||||
#include "tz.h"
|
||||
#include <iostream>
|
||||
|
||||
int
|
||||
main()
|
||||
{
|
||||
using namespace std::chrono;
|
||||
using namespace date;
|
||||
|
||||
auto nyc_tz = locate_zone("America/New_York");
|
||||
auto nyc_time = day_point(2004_y/oct/4) + 12h + 14min + 32s;
|
||||
std::cout << nyc_time << '\n';
|
||||
auto time_t_epoch = day_point(1970_y/1/1);
|
||||
std::cout << time_t_epoch << '\n';
|
||||
|
||||
// first convert nyc_time to utc via the utc_time()
|
||||
// call and subtract the ptime.
|
||||
auto sys_time = nyc_tz->to_sys(nyc_time);
|
||||
auto diff = sys_time - time_t_epoch;
|
||||
|
||||
// Expected 1096906472
|
||||
std::cout << "Seconds diff: " << diff.count() << '\n';
|
||||
|
||||
// Take leap seconds into account
|
||||
auto utc_time = utc_clock::sys_to_utc(sys_time);
|
||||
auto utc_epoc = utc_clock::sys_to_utc(time_t_epoch);
|
||||
diff = utc_time - utc_epoc;
|
||||
|
||||
// Expected 1096906494, an extra 22s
|
||||
std::cout << "Seconds diff: " << diff.count() << '\n';
|
||||
}
|
||||
Reference in New Issue
Block a user