src_corelib_time_qdatetime.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
#include <QDate>
#include <QTime>
#include <QTimeZone>
#include <chrono>
#include <iostream>
 
void examples()
{
    {
        //! [0]
        QDate d1(1995, 5, 17);  // May 17, 1995
        QDate d2(1995, 5, 20);  // May 20, 1995
        d1.daysTo(d2);          // returns 3
        d2.daysTo(d1);          // returns -3
        //! [0]
    }
 
    {
        //! [1]
        QDate date = QDate::fromString("1MM12car2003", "d'MM'MMcaryyyy");
        // date is 1 December 2003
        //! [1]
    }
 
    {
        //! [2]
        QDate date = QDate::fromString("130", "Md"); // invalid
        //! [2]
    }
 
    {
        //! [3]
        QDate::fromString("1.30", "M.d");           // January 30 1900
        QDate::fromString("20000110", "yyyyMMdd");  // January 10, 2000
        QDate::fromString("20000110", "yyyyMd");    // January 10, 2000
        //! [3]
    }
 
    {
        //! [4]
        QDate::isValid(2002, 5, 17);  // true
        QDate::isValid(2002, 2, 30);  // false (Feb 30 does not exist)
        QDate::isValid(2004, 2, 29);  // true (2004 is a leap year)
        QDate::isValid(2000, 2, 29);  // true (2000 is a leap year)
        QDate::isValid(2006, 2, 29);  // false (2006 is not a leap year)
        QDate::isValid(2100, 2, 29);  // false (2100 is not a leap year)
        QDate::isValid(1202, 6, 6);   // true (even though 1202 is pre-Gregorian)
        //! [4]
    }
 
    {
        //! [5]
        QTime n(14, 0, 0);                // n == 14:00:00
        QTime t;
        t = n.addSecs(70);                // t == 14:01:10
        t = n.addSecs(-70);               // t == 13:58:50
        t = n.addSecs(10 * 60 * 60 + 5);  // t == 00:00:05
        t = n.addSecs(-15 * 60 * 60);     // t == 23:00:00
        //! [5]
    }
 
    {
        //! [6]
        QTime time = QTime::fromString("1mm12car00", "m'mm'hcarss");
        // time is 12:01.00
        //! [6]
    }
 
    {
        //! [7]
        QTime time = QTime::fromString("00:710", "hh:ms"); // invalid
        //! [7]
    }
 
    {
        //! [8]
        QTime time = QTime::fromString("1.30", "m.s");
        // time is 00:01:30.000
        //! [8]
    }
 
    {
        //! [9]
        QTime::isValid(21, 10, 30); // returns true
        QTime::isValid(22, 5,  62); // returns false
        //! [9]
    }
 
    {
        //! [11]
        QDateTime now = QDateTime::currentDateTime();
        QDateTime xmas(QDate(now.date().year(), 12, 25).startOfDay());
        qDebug("There are %d seconds to Christmas", now.secsTo(xmas));
        //! [11]
    }
 
    {
        //! [12]
        QTime time1 = QTime::fromString("131", "HHh");
        // time1 is 13:00:00
        QTime time2 = QTime::fromString("1apA", "1amAM");
        // time2 is 01:00:00
 
        QDateTime dateTime2 = QDateTime::fromString("M1d1y9800:01:02",
                                                    "'M'M'd'd'y'yyhh:mm:ss");
        // dateTime is 1 January 1998 00:01:02
        //! [12]
    }
 
    {
        //! [13]
        QDateTime dateTime = QDateTime::fromString("130", "Mm"); // invalid
        //! [13]
    }
 
    {
        //! [14]
        QDateTime dateTime = QDateTime::fromString("1.30.1", "M.d.s");
        // dateTime is January 30 in 1900 at 00:00:01.
        dateTime = QDateTime::fromString("12", "yy");
        // dateTime is January 1 in 1912 at 00:00:00.
        //! [14]
    }
 
    {
        //! [15]
        QDateTime startDate(QDate(2012, 7, 6), QTime(8, 30, 0));
        QDateTime endDate(QDate(2012, 7, 7), QTime(16, 30, 0));
        qDebug() << "Days from startDate to endDate: " << startDate.daysTo(endDate);
 
        startDate = QDateTime(QDate(2012, 7, 6), QTime(23, 55, 0));
        endDate = QDateTime(QDate(2012, 7, 7), QTime(0, 5, 0));
        qDebug() << "Days from startDate to endDate: " << startDate.daysTo(endDate);
 
        qSwap(startDate, endDate); // Make endDate before startDate.
        qDebug() << "Days from startDate to endDate: " << startDate.daysTo(endDate);
        //! [15]
    }
 
#if QT_DEPRECATED_SINCE(6, 9)
    {
        //! [16]
        QDateTime local(QDateTime::currentDateTime());
        QDateTime UTC(local.toTimeSpec(Qt::UTC));
        qDebug() << "Local time is:" << local;
        qDebug() << "UTC time is:" << UTC;
        qDebug() << "No difference between times:" << local.secsTo(UTC);
        //! [16]
    }
#endif // QT_DEPRECATED_SINCE(6, 9)
 
    {
        //! [17]
        QDateTime UTC(QDateTime::currentDateTimeUtc());
        QDateTime local(UTC.toLocalTime());
        qDebug() << "UTC time is:" << UTC;
        qDebug() << "Local time is:" << local;
        qDebug() << "No difference between times:" << UTC.secsTo(local);
        //! [17]
    }
 
    {
        //! [18]
        QDateTime local(QDateTime::currentDateTime());
        QDateTime UTC(local.toUTC());
        qDebug() << "Local time is:" << local;
        qDebug() << "UTC time is:" << UTC;
        qDebug() << "No difference between times:" << local.secsTo(UTC);
        //! [18]
    }
 
#if QT_DEPRECATED_SINCE(6, 9)
    {
        //! [19]
        QDateTime local(QDateTime::currentDateTime());
        qDebug() << "Local time is:" << local;
 
        QDateTime UTC(local);
        UTC.setTimeSpec(Qt::UTC);
        qDebug() << "UTC time is:" << UTC;
 
        qDebug() << "There are" << local.secsTo(UTC) << "seconds difference between the datetimes.";
        //! [19]
    }
#endif // QT_DEPRECATED_SINCE(6, 9)
 
#if defined(__cpp_lib_crono) && __cpp_lib_crono > 201907L
    {
        using namespace std::chrono;
 
        //! [22]
        // 23 April 2012:
        QDate date = std::chrono::year_month_day(std::chrono::year(2012),
                                                std::chrono::month(4),
                                                std::chrono::day(23));
 
        // Same, under `using std::chrono` convenience:
        QDate dateWithLiterals1 = 23d / April / 2012y;
        QDate dateWithLiterals2 = 2012y / April / 23;
 
        // Last day of February 2000
        QDate lastDayFeb2020 = 2000y / February / last;
 
        // First Monday of January 2020:
        QDate firstMonday = 2020y / January / Monday[0];
 
        // Last Monday of January 2020:
        QDate lastMonday = 2020y / January / Monday[last];
        //! [22]
    }
#endif
 
    {
        //! [23]
        QDateTime local(QDateTime::currentDateTime());
        QDateTime UTC(local.toTimeZone(QTimeZone::UTC));
        qDebug() << "Local time is:" << local;
        qDebug() << "UTC time is:" << UTC;
        qDebug() << "No difference between times represented:" << local.secsTo(UTC);
        //! [23]
    }
}