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QDate Class Reference

The QDate class provides date functions. More...

All the functions in this class are reentrant when Qt is built with thread support.

#include <qdatetime.h>

List of all member functions.

Public Members

Static Public Members

Related Functions

Detailed Description

The QDate class provides date functions.

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 14th 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 )

Constructs a date with year y, month m and day 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

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().

QDate QDate::addMonths ( int nmonths ) const

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

See also addDays() and addYears().

QDate QDate::addYears ( int nyears ) const

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

See also addDays() and addMonths().

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

Returns the current date, as reported by the system clock, for the TimeSpec ts. The default TimeSpec is LocalTime.

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

Example: dclock/dclock.cpp.

QDate QDate::currentDate () [static]

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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

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

int QDate::day () const

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

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

Example: dclock/dclock.cpp.

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

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

Use shortDayName() instead.

int QDate::dayOfWeek () const

Returns the weekday (Monday=1..Sunday=7) for this date.

See also day() and dayOfYear().

int QDate::dayOfYear () const

Returns the day of the year (1..365) for this date.

See also day() and dayOfWeek().

int QDate::daysInMonth () const

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

See also day() and daysInYear().

int QDate::daysInYear () const

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

See also day() and daysInMonth().

int QDate::daysTo ( 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: 

        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]

Returns the QDate represented by the string s, using the format f, 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.

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

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

See also isNull().

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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]

Returns TRUE if the specified year y is a leap year; otherwise returns FALSE.

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

Returns the long name of the weekday.

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]

Returns the long name of the month.

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

Returns the month (January=1..December=12) of this date.

See also year() and day().

Example: dclock/dclock.cpp.

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

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

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 )

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

Returns the name of the weekday.

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]

Returns the name of the month.

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

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

These expressions may be used:

Expression Output
d the day as number without a leading zero (1-31)
dd the day as number with a leading zero (01-31)
ddd the abbreviated localized day name (e.g. 'Mon'..'Sun'). Uses QDate::shortDayName().
dddd the long localized day name (e.g. 'Monday'..'Sunday'). Uses QDate::longDayName().
M the month as number without a leading zero (1-12)
MM the month as number with a leading zero (01-12)
MMM the abbreviated localized month name (e.g. 'Jan'..'Dec'). Uses QDate::shortMonthName().
MMMM the long localized month name (e.g. 'January'..'December'). Uses QDate::longMonthName().
yy the year as two digit number (00-99)
yyyy the year as four digit number (1752-8000)

All other input characters will be ignored.

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

Format Result
dd.MM.yyyy 20.07.1969
ddd MMMM d yy Sun July 20 69

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

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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.

See also shortDayName() and shortMonthName().

int QDate::weekNumber ( 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.

See also isValid().

int QDate::year () const

Returns the year (1752..8000) of this date.

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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Qt version 3.1.2