QDate Class Reference

Detailed Description

A QDate object contains a calendar date, i.e. year, month, and day numbers, in the modern Western (Gregorian) calendar. It can read the current date from the system clock. It provides functions for comparing dates and for manipulating dates, e.g. by adding a number of days or months or years.

A QDate object is typically created either by giving the year, month and day numbers explicitly, or by using the static function currentDate(), which creates a QDate object containing the system clock's date. An explicit date can also be set using setYMD(). 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 leapYear() function indicates whether this date is in a leap year.

Note that QDate should not be used for date calculations for dates prior to the introduction of the Gregorian calendar. This calendar was adopted by England from the 14^th September 1752 (hence this is the earliest valid QDate), and subsequently by most other Western countries, until 1923.

The end of time is reached around the year 8000, by which time we expect Qt to be obsolete.

See also QTime, QDateTime, QDateEdit, QDateTimeEdit, and Time and Date.

Member Function Documentation

QDate::QDate ()

Constructs a null date. Null dates are invalid.

See also isNull() and isValid().

QDate::QDate ( int y, int m, int d )

y must be in the range 1752..8000, m must be in the range 1..12, and d must be in the range 1..31.

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

See also isValid().

QDate QDate::addDays ( int ndays ) const

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

QDate QDate::addMonths ( int nmonths ) const

See also addDays() and addYears().

QDate QDate::addYears ( int nyears ) const

See also addDays() and addMonths().

QDate QDate::currentDate ( Qt::TimeSpec ts ) [static]

See also QTime::currentTime(), QDateTime::currentDateTime(), and Qt::TimeSpec.

Example: dclock/dclock.cpp.

QDate QDate::currentDate () [static]

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

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

int QDate::day () const

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

Example: dclock/dclock.cpp.

QString QDate::dayName ( int weekday ) [static]

Use shortDayName() instead.

int QDate::dayOfWeek () const

See also day() and dayOfYear().

int QDate::dayOfYear () const

See also day() and dayOfWeek().

int QDate::daysInMonth () const

See also day() and daysInYear().

int QDate::daysInYear () const

See also day() and daysInMonth().

int QDate::daysTo ( const QDate & d ) const

Example:

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

See also addDays().

QDate QDate::fromString ( const QString & s, Qt::DateFormat f = Qt::TextDate ) [static]

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.

Warning: Qt::LocalDate cannot be used here.

bool QDate::isNull () const

Returns TRUE if the date is null; otherwise returns FALSE. A null date is invalid.

See also isValid().

bool QDate::isValid () const

See also isNull().

bool QDate::isValid ( int y, int m, int d ) [static]

Returns TRUE if the specified date (year y, month m and day d) is valid; otherwise returns FALSE.

Example:

    QDate::isValid( 2002, 5, 17 );  // TRUE   May 17th 2002 is valid
    QDate::isValid( 2002, 2, 30 );  // FALSE  Feb 30th does not exist
    QDate::isValid( 2004, 2, 29 );  // TRUE   2004 is a leap year
    QDate::isValid( 1202, 6, 6 );   // FALSE  1202 is pre-Gregorian
    

Warning: A y value in the range 00..99 is interpreted as 1900..1999.

See also isNull() and setYMD().

bool QDate::leapYear ( int y ) [static]

QString QDate::longDayName ( int weekday ) [static]

1 = "Monday", 2 = "Tuesday", ... 7 = "Sunday"

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

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

QString QDate::longMonthName ( int month ) [static]

1 = "January", 2 = "February", ... 12 = "December"

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

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

int QDate::month () const

See also year() and day().

Example: dclock/dclock.cpp.

QString QDate::monthName ( int month ) [static]

Use shortMonthName() instead.

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

Returns TRUE if this date is different from d; otherwise returns FALSE.

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

Returns TRUE if this date is earlier than d, otherwise returns FALSE.

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

Returns TRUE if this date is earlier than or equal to d, otherwise returns FALSE.

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

Returns TRUE if this date is equal to d; otherwise returns FALSE.

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

Returns TRUE if this date is later than d, otherwise returns FALSE.

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

Returns TRUE if this date is later than or equal to d, otherwise returns FALSE.

bool QDate::setYMD ( int y, int m, int d )

y must be in the range 1752..8000, m must be in the range 1..12, and d must be in the range 1..31.

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

Returns TRUE if the date is valid; otherwise returns FALSE.

QString QDate::shortDayName ( int weekday ) [static]

1 = "Mon", 2 = "Tue", ... 7 = "Sun"

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

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

QString QDate::shortMonthName ( int month ) [static]

1 = "Jan", 2 = "Feb", ... 12 = "Dec"

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

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

QString QDate::toString ( const QString & format ) const

These expressions may be used:

All other input characters will be ignored.

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

If the date is an invalid date, then QString::null will be returned.

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

QString QDate::toString ( Qt::DateFormat f = Qt::TextDate ) const

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

If f is Qt::TextDate, the string format is "Sat May 20 1995" (using the shortDayName() and shortMonthName() functions to generate the string, so the day and month names are locale specific).

If f is Qt::ISODate, the string format corresponds to the ISO 8601 specification for representations of dates, which is 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 f is Qt::LocalDate, the string format depends on the locale settings of the system.

If the date is an invalid date, then QString::null will be returned.

See also shortDayName() and shortMonthName().

int QDate::weekNumber ( int * yearNumber = 0 ) const

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.

See also isValid().

int QDate::year () const

See also month() and day().

Related Functions

QDataStream & operator<< ( QDataStream & s, const QDate & d )

Writes the date, d, to the data stream, s.

See also Format of the QDataStream operators.

QDataStream & operator>> ( QDataStream & s, QDate & d )

Reads a date from the stream s into d.

See also Format of the QDataStream operators.

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