QDate Class Reference

The QDate class provides date functions.

  1. #include <QDate>

Note: All functions in this class are reentrant.

Detailed Description

The QDate class provides date functions.

A QDate object contains a calendar date, i.e. year, month, and day numbers, in the Gregorian calendar. (see Use of Gregorian and Julian Calendars for dates prior to 15 October 1582). It can read the current date from the system clock. It provides functions for comparing dates, and for manipulating dates. For example, it is possible to add and subtract days, months, and years to dates.

A QDate object is typically created either by giving the year, month, and day numbers explicitly. Note that QDate interprets two digit years as is, i.e., years 0 - 99. A QDate can also be constructed with the static function currentDate(), which creates a QDate object containing the system clock's date. An explicit date can also be set using setDate(). The fromString() function returns a QDate given a string and a date format which is used to interpret the date within the string.

The year(), month(), and day() functions provide access to the year, month, and day numbers. Also, dayOfWeek() and dayOfYear() functions are provided. The same information is provided in textual format by the toString(), shortDayName(), longDayName(), shortMonthName(), and longMonthName() functions.

QDate provides a full set of operators to compare two QDate objects where smaller means earlier, and larger means later.

You can increment (or decrement) a date by a given number of days using addDays(). Similarly you can use addMonths() and addYears(). The daysTo() function returns the number of days between two dates.

The daysInMonth() and daysInYear() functions return how many days there are in this date's month and year, respectively. The isLeapYear() function indicates whether a date is in a leap year.

Use of Gregorian and Julian Calendars

QDate uses the Gregorian calendar in all locales, beginning on the date 15 October 1582. For dates up to and including 4 October 1582, the Julian calendar is used. This means there is a 10-day gap in the internal calendar between the 4th and the 15th of October 1582. When you use QDateTime for dates in that epoch, the day after 4 October 1582 is 15 October 1582, and the dates in the gap are invalid.

The Julian to Gregorian changeover date used here is the date when the Gregorian calendar was first introduced, by Pope Gregory XIII. That change was not universally accepted and some localities only executed it at a later date (if at all). QDateTime doesn't take any of these historical facts into account. If an application must support a locale-specific dating system, it must do so on its own, remembering to convert the dates using the Julian day.

No Year 0

There is no year 0. Dates in that year are considered invalid. The year -1 is the year "1 before Christ" or "1 before current era." The day before 0001-01-01 is December 31st, 1 BCE.

Range of Valid Dates

The range of valid dates is from January 2nd, 4713 BCE, to sometime in the year 11 million CE. The Julian Day returned by QDate::toJulianDay() is a number in the contiguous range from 1 to overflow, even across QDateTime's "date holes". It is suitable for use in applications that must convert a QDateTime to a date in another calendar system, e.g., Hebrew, Islamic or Chinese.

See also QTime, QDateTime, QDateEdit, QDateTimeEdit, and QCalendarWidget.

Public Types

Toggle detailsenum QDate::

MonthNameTypeMonthNameType { DateFormat , StandaloneFormat 1 ...} { DateFormat , StandaloneFormat 1 }

This enum describes the types of the string representation used for the month name.

ConstantValueDescription
QDate::DateFormat 0 This type of name can be used for date-to-string formatting.
QDate::StandaloneFormat 1 This type is used when you need to enumerate months or weekdays. Usually standalone names are represented in singular forms with capitalized first letter.

Look up this member in the source code.

    Public Functions

    Toggle details QDate

    QDateQDate () ()

    Constructs a null date. Null dates are invalid.

    See also isNull() and isValid().

    Look up this member in the source code.

    Toggle details QDate

    QDateQDate ( int y , int m , int d ) ( int y , int m , int d )

    Constructs a date with year y, month m and day d.

    If the specified date is invalid, the date is not set and isValid() returns false. A date before 2 January 4713 B.C. is considered invalid.

    Warning: Years 0 to 99 are interpreted as is, i.e., years 0-99.

    See also isValid().

    Look up this member in the source code.

    Toggle details QDate QDate

    addDaysaddDays ( int ndays ) ( int ndays )const

    Returns a QDate object containing a date ndays later than the date of this object (or earlier if ndays is negative).

    See also addMonths(), addYears(), and daysTo().

    Look up this member in the source code.

    Toggle details QDate QDate

    addMonthsaddMonths ( int nmonths ) ( int nmonths )const

    Returns a QDate object containing a date nmonths later than the date of this object (or earlier if nmonths is negative).

    Note: If the ending day/month combination does not exist in the resulting month/year, this function will return a date that is the latest valid date.

    Warning: QDate has a date hole around the days introducing the Gregorian calendar (the days 5 to 14 October 1582, inclusive, do not exist). If the calculation ends in one of those days, QDate will return either October 4 or October 15.

    See also addDays() and addYears().

    Look up this member in the source code.

    Toggle details QDate QDate

    addYearsaddYears ( int nyears ) ( int nyears )const

    Returns a QDate object containing a date nyears later than the date of this object (or earlier if nyears is negative).

    Note: If the ending day/month combination does not exist in the resulting year (i.e., if the date was Feb 29 and the final year is not a leap year), this function will return a date that is the latest valid date (that is, Feb 28).

    See also addDays() and addMonths().

    Look up this member in the source code.

    Toggle details QDate QDate

    currentDatecurrentDate () () [static]

    Returns the current date, as reported by the system clock.

    See also QTime::currentTime() and QDateTime::currentDateTime().

    Look up this member in the source code.

    Toggle details int QDate

    dayday () ()const

    Returns the day of the month (1 to 31) of this date.

    See also year(), month(), and dayOfWeek().

    Look up this member in the source code.

    Toggle details int QDate

    dayOfWeekdayOfWeek () ()const

    Returns the weekday (1 to 7) for this date.

    See also day(), dayOfYear(), and Qt::DayOfWeek.

    Look up this member in the source code.

    Toggle details int QDate

    dayOfYeardayOfYear () ()const

    Returns the day of the year (1 to 365 or 366 on leap years) for this date.

    See also day() and dayOfWeek().

    Look up this member in the source code.

    Toggle details int QDate

    daysInMonthdaysInMonth () ()const

    Returns the number of days in the month (28 to 31) for this date.

    See also day() and daysInYear().

    Look up this member in the source code.

    Toggle details int QDate

    daysInYeardaysInYear () ()const

    Returns the number of days in the year (365 or 366) for this date.

    See also day() and daysInMonth().

    Look up this member in the source code.

    Toggle details int QDate

    daysTodaysTo ( const QDate &d ) ( const QDate &d )const

    Returns the number of days from this date to d (which is negative if d is earlier than this date).

    Example:

    1.                     QDate d1(1995, 5, 17);  // May 17, 1995
    2. QDate d2(1995, 5, 20);  // May 20, 1995
    3. d1.daysTo(d2);          // returns 3
    4. d2.daysTo(d1);          // returns -3

    See also addDays().

    Look up this member in the source code.

    Toggle details QDate QDate

    fromJulianDayfromJulianDay ( int jd ) ( int jd ) [static]

    Converts the Julian day jd to a QDate.

    See also toJulianDay().

    Look up this member in the source code.

    Toggle details QDate QDate

    fromStringfromString ( const QString &string , Qt::DateFormat format=Qt::TextDate ...) ( const QString &string , Qt::DateFormat format=Qt::TextDate ) [static]

    Returns the QDate represented by the string, using the format given, or an invalid date if the string cannot be parsed.

    Note for Qt::TextDate: It is recommended that you use the English short month names (e.g. "Jan"). Although localized month names can also be used, they depend on the user's locale settings.

    Look up this member in the source code.

    Toggle details QDate QDate

    fromStringfromString ( const QString &string , const QString &format ...) ( const QString &string , const QString &format ) [static]

    Returns the QDate represented by the string, using the format given, or an invalid date if the string cannot be parsed.

    These expressions may be used for the format:

    ExpressionOutput
    dThe day as a number without a leading zero (1 to 31)
    ddThe day as a number with a leading zero (01 to 31)
    dddThe abbreviated localized day name (e.g. 'Mon' to 'Sun'). Uses QDate::shortDayName().
    ddddThe long localized day name (e.g. 'Monday' to 'Sunday'). Uses QDate::longDayName().
    MThe month as a number without a leading zero (1 to 12)
    MMThe month as a number with a leading zero (01 to 12)
    MMMThe abbreviated localized month name (e.g. 'Jan' to 'Dec'). Uses QDate::shortMonthName().
    MMMMThe long localized month name (e.g. 'January' to 'December'). Uses QDate::longMonthName().
    yyThe year as two digit number (00 to 99)
    yyyyThe year as four digit number. If the year is negative, a minus sign is prepended in addition.

    All other input characters will be treated as text. Any sequence of characters that are enclosed in single quotes will also be treated as text and will not be used as an expression. For example:

    1.                     QDate date = QDate::fromString("1MM12car2003", "d'MM'MMcaryyyy");
    2. // date is 1 December 2003

    If the format is not satisfied, an invalid QDate is returned. The expressions that don't expect leading zeroes (d, M) will be greedy. This means that they will use two digits even if this will put them outside the accepted range of values and leaves too few digits for other sections. For example, the following format string could have meant January 30 but the M will grab two digits, resulting in an invalid date:

    1.                     QDate date = QDate::fromString("130", "Md"); // invalid

    For any field that is not represented in the format the following defaults are used:

    FieldDefault value
    Year1900
    Month1
    Day1

    The following examples demonstrate the default values:

    1.                     QDate::fromString("1.30", "M.d");           // January 30 1900
    2. QDate::fromString("20000110", "yyyyMMdd");  // January 10, 2000
    3. QDate::fromString("20000110", "yyyyMd");    // January 10, 2000

    See also QDateTime::fromString(), QTime::fromString(), QDate::toString(), QDateTime::toString(), and QTime::toString().

    Look up this member in the source code.

    Toggle details void QDate

    getDategetDate ( int *year , int *month , int *day ) ( int *year , int *month , int *day )

    Extracts the date's year, month, and day, and assigns them to *year, *month, and *day. The pointers may be null.

    See also year(), month(), day(), and isValid().

    Look up this member in the source code.

    Toggle details bool QDate

    isLeapYearisLeapYear ( int year ) ( int year ) [static]

    Returns true if the specified year is a leap year; otherwise returns false.

    Look up this member in the source code.

    Toggle details bool QDate

    isNullisNull () ()const

    Returns true if the date is null; otherwise returns false. A null date is invalid.

    Note: The behavior of this function is equivalent to isValid().

    See also isValid().

    Look up this member in the source code.

    Toggle details bool QDate

    isValidisValid () ()const

    Returns true if this date is valid; otherwise returns false.

    See also isNull().

    Look up this member in the source code.

    Toggle details bool QDate

    isValidisValid ( int year , int month , int day ) ( int year , int month , int day ) [static]

    This is an overloaded function.

    Returns true if the specified date (year, month, and day) is valid; otherwise returns false.

    Example:

    1.                     QDate::isValid(2002, 5, 17);  // true
    2. QDate::isValid(2002, 2, 30);  // false (Feb 30 does not exist)
    3. QDate::isValid(2004, 2, 29);  // true (2004 is a leap year)
    4. QDate::isValid(2000, 2, 29);  // true (2000 is a leap year)
    5. QDate::isValid(2006, 2, 29);  // false (2006 is not a leap year)
    6. QDate::isValid(2100, 2, 29);  // false (2100 is not a leap year)
    7. QDate::isValid(1202, 6, 6);   // true (even though 1202 is pre-Gregorian)

    See also isNull() and setDate().

    Look up this member in the source code.

    Toggle details QString QDate

    longDayNamelongDayName ( int weekday ) ( int weekday ) [static]

    Returns the long version of the name of the weekday. The returned name is in normal type which can be used for date formatting.

    See also toString(), shortDayName(), shortMonthName(), and longMonthName().

    Look up this member in the source code.

    Toggle details QString QDate

    longDayNamelongDayName ( int weekday , MonthNameType type ...) ( int weekday , MonthNameType type ) [static]

    Returns the long name of the weekday for the representation specified by type.

    The days are enumerated using the following convention:

    • 1 = "Monday"
    • 2 = "Tuesday"
    • 3 = "Wednesday"
    • 4 = "Thursday"
    • 5 = "Friday"
    • 6 = "Saturday"
    • 7 = "Sunday"

    The day names will be localized according to the system's locale settings.

    See also toString(), shortDayName(), shortMonthName(), and longMonthName().

    Look up this member in the source code.

    Toggle details QString QDate

    longMonthNamelongMonthName ( int month ) ( int month ) [static]

    Returns the long version of the name of the month. The returned name is in normal type which can be used for date formatting.

    See also toString(), shortMonthName(), shortDayName(), and longDayName().

    Look up this member in the source code.

    Toggle details QString QDate

    longMonthNamelongMonthName ( int month , MonthNameType type ...) ( int month , MonthNameType type ) [static]

    Returns the long name of the month for the representation specified by type.

    The months are enumerated using the following convention:

    • 1 = "January"
    • 2 = "February"
    • 3 = "March"
    • 4 = "April"
    • 5 = "May"
    • 6 = "June"
    • 7 = "July"
    • 8 = "August"
    • 9 = "September"
    • 10 = "October"
    • 11 = "November"
    • 12 = "December"

    The month names will be localized according to the system's locale settings.

    See also toString(), shortMonthName(), shortDayName(), and longDayName().

    Look up this member in the source code.

    Toggle details int QDate

    monthmonth () ()const

    Returns the number corresponding to the month of this date, using the following convention:

    • 1 = "January"
    • 2 = "February"
    • 3 = "March"
    • 4 = "April"
    • 5 = "May"
    • 6 = "June"
    • 7 = "July"
    • 8 = "August"
    • 9 = "September"
    • 10 = "October"
    • 11 = "November"
    • 12 = "December"

    See also year() and day().

    Look up this member in the source code.

    Toggle details bool QDate

    setDatesetDate ( int year , int month , int day ) ( int year , int month , int day )

    Sets the date's year, month, and day. Returns true if the date is valid; otherwise returns false.

    If the specified date is invalid, the QDate object is set to be invalid. Any date before 2 January 4713 B.C. is considered invalid.

    See also isValid().

    Look up this member in the source code.

    Toggle details QString QDate

    shortDayNameshortDayName ( int weekday ) ( int weekday ) [static]

    Returns the short version of the name of the weekday. The returned name is in normal type which can be used for date formatting.

    See also toString(), longDayName(), shortMonthName(), and longMonthName().

    Look up this member in the source code.

    Toggle details QString QDate

    shortDayNameshortDayName ( int weekday , MonthNameType type ...) ( int weekday , MonthNameType type ) [static]

    Returns the short name of the weekday for the representation specified by type.

    The days are enumerated using the following convention:

    • 1 = "Mon"
    • 2 = "Tue"
    • 3 = "Wed"
    • 4 = "Thu"
    • 5 = "Fri"
    • 6 = "Sat"
    • 7 = "Sun"

    The day names will be localized according to the system's locale settings.

    See also toString(), shortMonthName(), longMonthName(), and longDayName().

    Look up this member in the source code.

    Toggle details QString QDate

    shortMonthNameshortMonthName ( int month ) ( int month ) [static]

    Returns the short version of the name of the month. The returned name is in normal type which can be used for date formatting.

    See also toString(), longMonthName(), shortDayName(), and longDayName().

    Look up this member in the source code.

    Toggle details QString QDate

    shortMonthNameshortMonthName ( int month , MonthNameType type ...) ( int month , MonthNameType type ) [static]

    Returns the short name of the month for the representation specified by type.

    The months are enumerated using the following convention:

    • 1 = "Jan"
    • 2 = "Feb"
    • 3 = "Mar"
    • 4 = "Apr"
    • 5 = "May"
    • 6 = "Jun"
    • 7 = "Jul"
    • 8 = "Aug"
    • 9 = "Sep"
    • 10 = "Oct"
    • 11 = "Nov"
    • 12 = "Dec"

    The month names will be localized according to the system's locale settings.

    See also toString(), longMonthName(), shortDayName(), and longDayName().

    Look up this member in the source code.

    Toggle details int QDate

    toJulianDaytoJulianDay () ()const

    Converts the date to a Julian day.

    See also fromJulianDay().

    Look up this member in the source code.

    Toggle details QString QDate

    toStringtoString ( const QString &format ) ( const QString &format )const

    Returns the date as a string. The format parameter determines the format of the result string.

    These expressions may be used:

    ExpressionOutput
    dthe day as number without a leading zero (1 to 31)
    ddthe day as number with a leading zero (01 to 31)
    dddthe abbreviated localized day name (e.g. 'Mon' to 'Sun'). Uses QDate::shortDayName().
    ddddthe long localized day name (e.g. 'Monday' to 'Sunday'). Uses QDate::longDayName().
    Mthe month as number without a leading zero (1 to 12)
    MMthe month as number with a leading zero (01 to 12)
    MMMthe abbreviated localized month name (e.g. 'Jan' to 'Dec'). Uses QDate::shortMonthName().
    MMMMthe long localized month name (e.g. 'January' to 'December'). Uses QDate::longMonthName().
    yythe year as two digit number (00 to 99)
    yyyythe year as four digit number. If the year is negative, a minus sign is prepended in addition.

    All other input characters will be ignored. Any sequence of characters that are enclosed in singlequotes will be treated as text and not be used as an expression. Two consecutive singlequotes ("''") are replaced by a singlequote in the output.

    Example format strings (assuming that the QDate is the 20 July 1969):

    FormatResult
    dd.MM.yyyy20.07.1969
    ddd MMMM d yySun July 20 69
    'The day is' ddddThe day is Sunday

    If the datetime is invalid, an empty string will be returned.

    Warning: The Qt::ISODate format is only valid for years in the range 0 to 9999. This restriction may apply to locale-aware formats as well, depending on the locale settings.

    See also QDateTime::toString() and QTime::toString().

    Look up this member in the source code.

    Toggle details QString QDate

    toStringtoString ( Qt::DateFormat format=Qt::TextDate ...) ( Qt::DateFormat format=Qt::TextDate )const

    This is an overloaded function.

    Returns the date as a string. The format parameter determines the format of the string.

    If the format is Qt::TextDate, the string is formatted in the default way. QDate::shortDayName() and QDate::shortMonthName() are used to generate the string, so the day and month names will be localized names. An example of this formatting is "Sat May 20 1995".

    If the format is Qt::ISODate, the string format corresponds to the ISO 8601 extended specification for representations of dates and times, taking the form YYYY-MM-DD, where YYYY is the year, MM is the month of the year (between 01 and 12), and DD is the day of the month between 01 and 31.

    If the format is Qt::SystemLocaleShortDate or Qt::SystemLocaleLongDate, the string format depends on the locale settings of the system. Identical to calling QLocale::system().toString(date, QLocale::ShortFormat) or QLocale::system().toString(date, QLocale::LongFormat).

    If the format is Qt::DefaultLocaleShortDate or Qt::DefaultLocaleLongDate, the string format depends on the default application locale. This is the locale set with QLocale::setDefault(), or the system locale if no default locale has been set. Identical to calling QLocale().toString(date, QLocale::ShortFormat) or QLocale().toString(date, QLocale::LongFormat).

    If the date is invalid, an empty string will be returned.

    Warning: The Qt::ISODate format is only valid for years in the range 0 to 9999. This restriction may apply to locale-aware formats as well, depending on the locale settings.

    See also shortDayName() and shortMonthName().

    Look up this member in the source code.

    Toggle details int QDate

    weekNumberweekNumber ( int *yearNumber=0 ) ( int *yearNumber=0 )const

    Returns the week number (1 to 53), and stores the year in *yearNumber unless yearNumber is null (the default).

    Returns 0 if the date is invalid.

    In accordance with ISO 8601, weeks start on Monday and the first Thursday of a year is always in week 1 of that year. Most years have 52 weeks, but some have 53.

    *yearNumber is not always the same as year(). For example, 1 January 2000 has week number 52 in the year 1999, and 31 December 2002 has week number 1 in the year 2003.

    Copyright (c) 1989 The Regents of the University of California. All rights reserved.

    Redistribution and use in source and binary forms are permitted provided that the above copyright notice and this paragraph are duplicated in all such forms and that any documentation, advertising materials, and other materials related to such distribution and use acknowledge that the software was developed by the University of California, Berkeley. The name of the University may not be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

    See also isValid().

    Look up this member in the source code.

    Toggle details int QDate

    yearyear () ()const

    Returns the year of this date. Negative numbers indicate years before 1 A.D. = 1 C.E., such that year -44 is 44 B.C.

    See also month() and day().

    Look up this member in the source code.

    Toggle details bool QDate

    operator!=operator!= ( const QDate &d ) ( const QDate &d )const

    Returns true if this date is different from d; otherwise returns false.

    Look up this member in the source code.

    Toggle details bool QDate

    operator<operator< ( const QDate &d ) ( const QDate &d )const

    Returns true if this date is earlier than d; otherwise returns false.

    Look up this member in the source code.

    Toggle details bool QDate

    operator<=operator<= ( const QDate &d ) ( const QDate &d )const

    Returns true if this date is earlier than or equal to d; otherwise returns false.

    Look up this member in the source code.

    Toggle details bool QDate

    operator==operator== ( const QDate &d ) ( const QDate &d )const

    Returns true if this date is equal to d; otherwise returns false.

    Look up this member in the source code.

    Toggle details bool QDate

    operator>operator> ( const QDate &d ) ( const QDate &d )const

    Returns true if this date is later than d; otherwise returns false.

    Look up this member in the source code.

    Toggle details bool QDate

    operator>=operator>= ( const QDate &d ) ( const QDate &d )const

    Returns true if this date is later than or equal to d; otherwise returns false.

    Look up this member in the source code.

    Toggle details bool QDate

    setYMDsetYMD ( int y , int m , int d ) ( int y , int m , int d ) Obsolete function

    Sets the date's year y, month m, and day d.

    If y is in the range 0 to 99, it is interpreted as 1900 to 1999.

    Use setDate() instead.

    Look up this member in the source code.

    Toggle details QDate QDate

    currentDatecurrentDate ( Qt::TimeSpec spec ) ( Qt::TimeSpec spec ) [static] Qt3-support

    If spec is Qt::LocalTime, use the currentDate() overload that takes no parameters instead; otherwise, use QDateTime::currentDateTime().

    For example, if you have code like

    1. QDate localDate = QDate::currentDate(Qt::LocalTime);
    2. QDate utcDate = QDate::currentDate(Qt::UTC);

    you can rewrite it as

    1.                     QDate localDate = QDate::currentDate();
    2. QDate utcDate = QDateTime::currentDateTime().toUTC().date();

    See also QDateTime::toUTC().

    Look up this member in the source code.

    Toggle details QString QDate

    dayNamedayName ( int weekday ) ( int weekday ) [static] Qt3-support

    Use shortDayName() instead.

    Look up this member in the source code.

    Toggle details bool QDate

    leapYearleapYear ( int year ) ( int year ) [static] Qt3-support

    Use isLeapYear() instead.

    Look up this member in the source code.

    Toggle details QString QDate

    monthNamemonthName ( int month ) ( int month ) [static] Qt3-support

    Use shortMonthName() instead.

    Look up this member in the source code.

    Notes provided by the Qt Community
    Informative
    • 0

    Votes: 0

    Coverage: Qt library 4.7, Qt 4.8

    Picture of Diluka Diluka

    Hobby Entomologist
    23 notes

    How to use QDate and QTime together

    First remember use to QDateTime library

    1. #include <QDateTime>

    Then use that command for implement the code for get date and time for your application

    1. //get current date
    2. QDate date = QDate::currentDate();
    3. QString dateString = date.toString();  
    4. ui.label->setText("Date: " + dateString);
    5.        
    6. //get current time
    7. QTime time = QTime::currentTime();
    8. QString timeString = time.toString();  
    9. ui.label_2->setText("Time: " + timeString);
    10.  
    11. //get current date and time
    12. QDateTime dateTime = QDateTime::currentDateTime();     
    13. QString dateTimeString = dateTime.toString();  
    14. ui.label_3->setText("Date and Time: " + dateTimeString);

    [Revisions]