CopperSpice API  1.7.2
QDate Class Reference

Provides date functions. More...

Public Types

enum  MonthNameType
 

Public Methods

constexpr QDate ()
 
 QDate (int y, int m, int d)
 
QDate addDays (qint64 days) const
 
QDate addMonths (qint64 months) const
 
QDate addYears (qint64 years) const
 
int day () const
 
int dayOfWeek () const
 
int dayOfYear () const
 
int daysInMonth () const
 
int daysInYear () const
 
qint64 daysTo (const QDate &value) const
 
void getDate (int *year, int *month, int *day)
 
bool isNull () const
 
bool isValid () const
 
int month () const
 
bool operator!= (const QDate &value) const
 
bool operator< (const QDate &value) const
 
bool operator<= (const QDate &value) const
 
bool operator== (const QDate &value) const
 
bool operator> (const QDate &value) const
 
bool operator>= (const QDate &value) const
 
bool setDate (int year, int month, int day)
 
constexpr qint64 toJulianDay () const
 
QString toString (const QString &format) const
 
QString toString (Qt::DateFormat format=Qt::TextDate) const
 
int weekNumber (int *yearNumber=nullptr) const
 
int year () const
 

Static Public Methods

static QDate currentDate ()
 
static constexpr QDate fromJulianDay (qint64 dayNumber)
 
static QDate fromString (const QString &str, const QString &format)
 
static QDate fromString (const QString &str, Qt::DateFormat format=Qt::TextDate)
 
static bool isLeapYear (int year)
 
static bool isValid (int year, int month, int day)
 
static QString longDayName (int weekday, MonthNameType type=DateFormat)
 
static QString longMonthName (int month, MonthNameType type=DateFormat)
 
static QString shortDayName (int weekday, MonthNameType type=DateFormat)
 
static QString shortMonthName (int month, MonthNameType type=DateFormat)
 

Friends

QDataStreamoperator<< (QDataStream &, const QDate &)
 
QDataStreamoperator>> (QDataStream &, QDate &)
 
class QDateTime
 

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. (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 does not 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, QCalendarWidget

Member Enumeration Documentation

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

ConstantValueDescription
QDate::DateFormat 0This type of name can be used for date-to-string formatting.
QDate::StandaloneFormat1 This type is used when you need to enumerate months or weekdays. Usually standalone names are represented in singular forms with capitalized first letter.

Constructor & Destructor Documentation

constexpr QDate::QDate ( )
inlineconstexpr

Constructs a null date. Null dates are invalid.

See also
isNull(), isValid()
QDate::QDate ( 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()

Method Documentation

QDate QDate::addDays ( qint64  days) const
nodiscard

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

See also
addMonths(), addYears(), daysTo()
QDate QDate::addMonths ( qint64  months) const
nodiscard

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

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(), addYears()
QDate QDate::addYears ( qint64  years) const
nodiscard

Returns a QDate object containing a date years later than the date of this object (or earlier if years 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(), addMonths()
QDate QDate::currentDate ( )
static

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

See also
QTime::currentTime(), QDateTime::currentDateTime()
int QDate::day ( ) const

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

See also
year(), month(), dayOfWeek()
int QDate::dayOfWeek ( ) const

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

See also
day(), dayOfYear(), Qt::DayOfWeek
int QDate::dayOfYear ( ) const

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

See also
day(), dayOfWeek()
int QDate::daysInMonth ( ) const

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

See also
day(), daysInYear()
int QDate::daysInYear ( ) const

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

See also
day(), daysInMonth()
qint64 QDate::daysTo ( const QDate &  value) const

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

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
See also
addDays()
constexpr QDate QDate::fromJulianDay ( qint64  dayNumber)
inlinestaticconstexpr

Converts the Julian day dayNumber to a QDate.

See also
toJulianDay()
QDate QDate::fromString ( const QString str,
const QString format 
)
static

Returns the QDate represented by the str, using the format given, or an invalid date if the string can not 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:

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

If the format is not satisfied, an invalid QDate is returned. The expressions that do not 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:

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:

QDate::fromString("1.30", "M.d"); // January 30 1900
QDate::fromString("20000110", "yyyyMMdd"); // January 10, 2000
QDate::fromString("20000110", "yyyyMd"); // January 10, 2000
See also
QDateTime::fromString(), QTime::fromString(), QDate::toString(), QDateTime::toString(), QTime::toString()
QDate QDate::fromString ( const QString str,
Qt::DateFormat  format = Qt::TextDate 
)
static

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

For Qt::TextDate it is recommended 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.

void QDate::getDate ( 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(), isValid()
bool QDate::isLeapYear ( int  year)
static

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

bool QDate::isNull ( ) const
inline

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

Note
The behavior of this method is equivalent to isValid().
See also
isValid()
bool QDate::isValid ( ) const
inline

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

See also
isNull()
bool QDate::isValid ( int  year,
int  month,
int  day 
)
static

Returns true if the specified year, month, and day are valid, otherwise returns false.

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)
See also
isNull(), setDate()
QString QDate::longDayName ( int  weekday,
MonthNameType  type = DateFormat 
)
static

Returns the long name of the weekday for the representation specified by type. The day names will be localized according to the system's default locale settings. Returns an empty string if the date is invalid.

The days are enumerated using the following convention:

  • 1 = "Monday"
  • 2 = "Tuesday"
  • 3 = "Wednesday"
  • 4 = "Thursday"
  • 5 = "Friday"
  • 6 = "Saturday"
  • 7 = "Sunday"
See also
toString(), shortDayName(), shortMonthName(), longMonthName()
QString QDate::longMonthName ( int  month,
MonthNameType  type = DateFormat 
)
static

Returns the long name of the month for the representation specified by type. The month names will be localized according to the system's default locale settings. Returns an empty string if the date is invalid.

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"
See also
toString(), shortMonthName(), shortDayName(), longDayName()
int QDate::month ( ) 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(), day()
bool QDate::operator!= ( const QDate &  value) const
inline

Returns true if this date is different from value, otherwise returns false.

bool QDate::operator< ( const QDate &  value) const
inline

Returns true if this date is earlier than value, otherwise returns false.

bool QDate::operator<= ( const QDate &  value) const
inline

Returns true if this date is earlier than or equal to value, otherwise returns false.

bool QDate::operator== ( const QDate &  value) const
inline

Returns true if this date is equal to value, otherwise returns false.

bool QDate::operator> ( const QDate &  value) const
inline

Returns true if this date is later than value, otherwise returns false.

bool QDate::operator>= ( const QDate &  value) const
inline

Returns true if this date is later than or equal to value, otherwise returns false.

bool QDate::setDate ( 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()
QString QDate::shortDayName ( int  weekday,
MonthNameType  type = DateFormat 
)
static

Returns the short name of the weekday for the representation specified by type. The day names will be localized according to the system's default locale settings. Returns an empty string if the date is invalid.

The days are enumerated using the following convention:

  • 1 = "Mon"
  • 2 = "Tue"
  • 3 = "Wed"
  • 4 = "Thu"
  • 5 = "Fri"
  • 6 = "Sat"
  • 7 = "Sun"
See also
toString(), shortMonthName(), longMonthName(), longDayName()
QString QDate::shortMonthName ( int  month,
MonthNameType  type = DateFormat 
)
static

Returns the short name of the month for the representation specified by type. The month names will be localized according to the system's default locale settings. Returns an empty string if the date is invalid.

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"
See also
toString(), longMonthName(), shortDayName(), longDayName()
constexpr qint64 QDate::toJulianDay ( ) const
inlineconstexpr

Converts the date to a Julian day.

See also
fromJulianDay()
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:

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.yyyy 20.07.1969
ddd MMMM d yy Sun July 20 69
'The day is' dddd The 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(), QTime::toString()
QString QDate::toString ( Qt::DateFormat  format = Qt::TextDate) const

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 using the default locale from the system. An example of this formatting is "Sat May 20 1995".

If theformat 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(), shortMonthName()
int QDate::weekNumber ( int *  yearNumber = nullptr) 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.

The value for 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 of this date. Negative numbers indicate years before 1 CE, such that year -44 is 44 BCE.

Returns 0 if the date is invalid.

See also
month(), day()

Friends And Related Function Documentation

QDataStream & operator<< ( QDataStream out,
const QDate &  value 
)
friend

Writes the value to stream out.

Refer to Serializing Data Types for additional information.

QDataStream & operator>> ( QDataStream in,
QDate &  value 
)
friend

Reads a date from stream in into the value.

Refer to Serializing Data Types for additional information.