QDate Class

The QDate class provides date functions. 更多...

头：	#include <QDate>
CMake:	find_package(Qt6 REQUIRED COMPONENTS Core) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core

此类 强烈可比较 .

此类 强烈可比较 with std::chrono::year_month_day, std::chrono::year_month_day_last, std::chrono::year_month_weekday, and std::chrono::year_month_weekday_last.

These comparison operators are only available when using C++20.

注意： 此类的所有函数可重入 .

公共函数

	QDate ()
	QDate (int y , int m , int d )
`(从 6.4 起)`	QDate (std::chrono::year_month_day date )
`(从 6.4 起)`	QDate (std::chrono::year_month_day_last date )
`(从 6.4 起)`	QDate (std::chrono::year_month_weekday date )
`(从 6.4 起)`	QDate (std::chrono::year_month_weekday_last date )
QDate	addDays (qint64 ndays ) const
`(从 6.4 起)` QDate	addDuration (std::chrono::days ndays ) const
QDate	addMonths (int nmonths , QCalendar cal ) const
QDate	addMonths (int nmonths ) const
QDate	addYears (int nyears , QCalendar cal ) const
QDate	addYears (int nyears ) const
int	day (QCalendar cal ) const
int	day () const
int	dayOfWeek (QCalendar cal ) const
int	dayOfWeek () const
int	dayOfYear (QCalendar cal ) const
int	dayOfYear () const
int	daysInMonth (QCalendar cal ) const
int	daysInMonth () const
int	daysInYear (QCalendar cal ) const
int	daysInYear () const
qint64	daysTo (QDate d ) const
QDateTime	endOfDay (const QTimeZone & zone ) const
`(从 6.5 起)` QDateTime	endOfDay () const
void	getDate (int * year , int * month , int * day ) const
bool	isNull () const
bool	isValid () const
int	month (QCalendar cal ) const
int	month () const
bool	setDate (int year , int month , int day )
bool	setDate (int year , int month , int day , QCalendar cal )
QDateTime	startOfDay (const QTimeZone & zone ) const
`(从 6.5 起)` QDateTime	startOfDay () const
qint64	toJulianDay () const
std::chrono::sys_days	toStdSysDays () const
QString	toString (const QString & format , QCalendar cal ) const
QString	toString (Qt::DateFormat format = Qt::TextDate) const
QString	toString (const QString & format ) const
QString	toString (QStringView format ) const
QString	toString (QStringView format , QCalendar cal ) const
int	weekNumber (int * yearNumber = nullptr) const
int	year (QCalendar cal ) const
int	year () const

静态公共成员

QDate	currentDate ()
QDate	fromJulianDay (qint64 jd )
`(从 6.4 起)` QDate	fromStdSysDays (const std::chrono::sys_days & days )
QDate	fromString (const QString & string , Qt::DateFormat format = Qt::TextDate)
`(从 6.0 起)` QDate	fromString (QStringView string , Qt::DateFormat format = Qt::TextDate)
`(从 6.0 起)` QDate	fromString (QStringView string , QStringView format , QCalendar cal )
`(从 6.0 起)` QDate	fromString (const QString & string , QStringView format , QCalendar cal )
QDate	fromString (const QString & string , const QString & format , QCalendar cal )
`(从 6.7 起)` QDate	fromString (QStringView string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)
`(从 6.7 起)` QDate	fromString (QStringView string , QStringView format , int baseYear , QCalendar cal )
`(从 6.7 起)` QDate	fromString (const QString & string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)
`(从 6.0 起)` QDate	fromString (const QString & string , QStringView format , int baseYear , QCalendar cal )
`(从 6.7 起)` QDate	fromString (const QString & string , const QString & format , int baseYear = QLocale::DefaultTwoDigitBaseYear)
QDate	fromString (const QString & string , const QString & format , int baseYear , QCalendar cal )
bool	isLeapYear (int year )
bool	isValid (int year , int month , int day )

bool	operator!= (const QDate & lhs , const QDate & rhs )
bool	operator< (const QDate & lhs , const QDate & rhs )
QDataStream &	operator<< (QDataStream & out , QDate date )
bool	operator<= (const QDate & lhs , const QDate & rhs )
bool	operator== (const QDate & lhs , const QDate & rhs )
bool	operator> (const QDate & lhs , const QDate & rhs )
bool	operator>= (const QDate & lhs , const QDate & rhs )
QDataStream &	operator>> (QDataStream & in , QDate & date )

详细描述

A QDate object represents a particular day, regardless of calendar, locale or other settings used when creating it or supplied by the system. It can report the year, month and day of the month that represent the day with respect to the proleptic Gregorian calendar or any calendar supplied as a QCalendar object. QDate objects should be passed by value rather than by reference to const; they simply package qint64 .

A QDate object is typically created by giving the year, month, and day numbers explicitly. Note that QDate interprets year numbers less than 100 as presented, i.e., as years 1 through 99, without adding any offset. The static function currentDate () creates a QDate object containing the date read from the system clock. An explicit date can also be set using setDate ()。 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 ()，和 day () functions provide access to the year, month, and day numbers. When more than one of these values is needed, it is more efficient to call QCalendar::partsFromDate (), to save repeating (potentially expensive) calendrical calculations.

Also, dayOfWeek () 和 dayOfYear () functions are provided. The same information is provided in textual format by toString (). QLocale can map the day numbers to names, QCalendar can map month numbers to names.

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 () 和 addYears ()。 daysTo () function returns the number of days between two dates.

The daysInMonth () 和 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. QCalendar can also supply this information, in some cases more conveniently.

备注

注意： All conversion to and from string formats is done using the C locale. For localized conversions, see QLocale .

In the Gregorian calendar, there is no year 0. Dates in that year are considered invalid. The year -1 is the year "1 before Christ" or "1 before common era." The day before 1 January 1 CE, QDate(1, 1, 1), is 31 December 1 BCE, QDate(-1, 12, 31). Various other calendars behave similarly; see QCalendar::hasYearZero ().

有效日期范围

Dates are stored internally as a Julian Day number, an integer count of every day in a contiguous range, with 24 November 4714 BCE in the Gregorian calendar being Julian Day 0 (1 January 4713 BCE in the Julian calendar). As well as being an efficient and accurate way of storing an absolute date, it is suitable for converting a date into other calendar systems such as Hebrew, Islamic or Chinese. The Julian Day number can be obtained using QDate::toJulianDay () and can be set using QDate::fromJulianDay ().

The range of Julian Day numbers that QDate can represent is, for technical reasons, limited to between -784350574879 and 784354017364, which means from before 2 billion BCE to after 2 billion CE. This is more than seven times as wide as the range of dates a QDateTime can represent.

另请参阅 QTime , QDateTime , QCalendar , QDateTime::YearRange , QDateEdit , QDateTimeEdit ，和 QCalendarWidget .

成员函数文档编制

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_day date )

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_day_last date )

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_weekday date )

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_weekday_last date )

构造 QDate representing the same date as date . This allows for easy interoperability between the Standard Library calendaring classes and Qt datetime classes.

例如：

// 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 = 23 / 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];

注意： 不像 QDate , std::chrono::year and the related classes feature the year zero. This means that if date is in the year zero or before, the resulting QDate object will have an year one less than the one specified by date .

注意： This function requires C++20.

该函数在 Qt 6.4 引入。

QString QDate:: toString ( QStringView format , QCalendar cal ) const

QString QDate:: toString (const QString & format , QCalendar cal ) const

Returns the date as a string. The format parameter determines the format of the result string. If cal is supplied, it determines the calendar used to represent the date; it defaults to Gregorian. Prior to Qt 5.14, there was no cal parameter and the Gregorian calendar was always used.

These expressions may be used in the format parameter:

表达式	输出
d	The day as a number without a leading zero (1 to 31)
dd	The day as a number with a leading zero (01 to 31)
ddd	The abbreviated day name ('Mon' to 'Sun').
dddd	The long day name ('Monday' to 'Sunday').
M	The month as a number without a leading zero (1 to 12)
MM	The month as a number with a leading zero (01 to 12)
MMM	The abbreviated month name ('Jan' to 'Dec').
MMMM	The long month name ('January' to 'December').
yy	The year as a two digit number (00 to 99)
yyyy	The year as a four digit number. If the year is negative, a minus sign is prepended, making five characters.

Any sequence of characters enclosed in single quotes will be included verbatim in the output string (stripped of the quotes), even if it contains formatting characters. Two consecutive single quotes ("''") are replaced by a single quote in the output. All other characters in the format string are included verbatim in the output string.

Formats without separators (e.g. "ddMM") are supported but must be used with care, as the resulting strings aren't always reliably readable (e.g. if "dM" produces "212" it could mean either the 2nd of December or the 21st of February).

格式字符串范例 (假定 QDate is the 20 July 1969):

格式	结果
dd.MM.yyyy	20.07.1969
ddd MMMM d yy	Sun July 20 69
'The day is' dddd	The day is Sunday

若日期时间无效，返回空字符串。

注意： Day and month names are given in English (C locale). To get localized month and day names, use QLocale::system (). toString ().

注意： If a format character is repeated more times than the longest expression in the table above using it, this part of the format will be read as several expressions with no separator between them; the longest above, possibly repeated as many times as there are copies of it, ending with a residue that may be a shorter expression. Thus 'MMMMMMMMMM' for a date in May will contribute "MayMay05" to the output.

另请参阅 fromString (), QDateTime::toString (), QTime::toString ()，和 QLocale::toString ().

`[constexpr]` QDate:: QDate ()

Constructs a null date. Null dates are invalid.

另请参阅 isNull () 和 isValid ().

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

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

The date is understood in terms of the Gregorian calendar. If the specified date is invalid, the date is not set and isValid () 返回 false .

警告： Years 1 to 99 are interpreted as is. Year 0 is invalid.

另请参阅 isValid () 和 QCalendar::dateFromParts ().

QDate QDate:: addDays ( qint64 ndays ) const

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

Returns a null date if the current date is invalid or the new date is out of range.

另请参阅 addMonths (), addYears ()，和 daysTo ().

`[since 6.4]` QDate QDate:: addDuration ( std::chrono::days ndays ) const

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

Returns a null date if the current date is invalid or the new date is out of range.

注意： Adding durations expressed in std::chrono::months or std::chrono::years does not yield the same result obtained by using addMonths () 或 addYears (). The former are fixed durations, calculated in relation to the solar year; the latter use the Gregorian calendar definitions of months/years.

注意： This function requires C++20.

该函数在 Qt 6.4 引入。

另请参阅 addMonths (), addYears ()，和 daysTo ().

QDate QDate:: addMonths ( int nmonths , QCalendar cal ) const

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

Uses cal as calendar, if supplied, else the Gregorian calendar.

注意： 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 in the selected month.

另请参阅 addDays () 和 addYears ().

QDate QDate:: addMonths ( int nmonths ) const

这是重载函数。

QDate QDate:: addYears ( int nyears , QCalendar cal ) const

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

Uses cal as calendar, if supplied, else the Gregorian calendar.

注意： If the ending day/month combination does not exist in the resulting year (e.g., for the Gregorian calendar, 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 in the given month (in the example, Feb 28).

另请参阅 addDays () 和 addMonths ().

QDate QDate:: addYears ( int nyears ) const

这是重载函数。

`[static]` QDate QDate:: currentDate ()

Returns the system clock's current date.

另请参阅 QTime::currentTime () 和 QDateTime::currentDateTime ().

int QDate:: day ( QCalendar cal ) const

Returns the day of the month for this date.

Uses cal as calendar if supplied, else the Gregorian calendar (for which the return ranges from 1 to 31). Returns 0 if the date is invalid.

另请参阅 year (), month (), dayOfWeek ()，和 QCalendar::partsFromDate ().

int QDate:: day () const

这是重载函数。

int QDate:: dayOfWeek ( QCalendar cal ) const

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

Uses cal as calendar if supplied, else the Gregorian calendar. Returns 0 if the date is invalid. Some calendars may give special meaning (e.g. intercallary days) to values greater than 7.

另请参阅 day (), dayOfYear (), QCalendar::dayOfWeek ()，和 Qt::DayOfWeek .

int QDate:: dayOfWeek () const

这是重载函数。

int QDate:: dayOfYear ( QCalendar cal ) const

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

Uses cal as calendar if supplied, else the Gregorian calendar. Returns 0 if either the date or the first day of its year is invalid.

另请参阅 day (), dayOfWeek ()，和 QCalendar::daysInYear ().

int QDate:: dayOfYear () const

这是重载函数。

int QDate:: daysInMonth ( QCalendar cal ) const

Returns the number of days in the month for this date.

Uses cal as calendar if supplied, else the Gregorian calendar (for which the result ranges from 28 to 31). Returns 0 if the date is invalid.

另请参阅 day (), daysInYear (), QCalendar::daysInMonth (), QCalendar::maximumDaysInMonth ()，和 QCalendar::minimumDaysInMonth ().

int QDate:: daysInMonth () const

这是重载函数。

int QDate:: daysInYear ( QCalendar cal ) const

Returns the number of days in the year for this date.

Uses cal as calendar if supplied, else the Gregorian calendar (for which the result is 365 or 366). Returns 0 if the date is invalid.

另请参阅 day (), daysInMonth (), QCalendar::daysInYear ()，和 QCalendar::maximumMonthsInYear ().

int QDate:: daysInYear () const

这是重载函数。

qint64 QDate:: daysTo ( QDate d ) const

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

Returns 0 if either date is invalid.

范例：

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

另请参阅 addDays ().

QDateTime QDate:: endOfDay (const QTimeZone & zone ) const

Returns the end-moment of the day.

When a day ends depends on a how time is described: each day starts and ends earlier for those in time-zones further west and later for those in time-zones further east. The time representation to use can be specified by an optional time zone . The default time representation is the system's local time.

Usually, the end of the day is one millisecond before the midnight, 24:00: however, if a time-zone transition causes the given date to skip over that moment (e.g. a DST spring-forward skipping over 23:00 and the following hour), the actual latest time in the day is returned. This can only arise when the time representation is a time-zone or local time.

当 zone has a timeSpec() of Qt::OffsetFromUTC or Qt::UTC , the time representation has no transitions so the end of the day is QTime (23, 59, 59, 999).

In the rare case of a date that was entirely skipped (this happens when a zone east of the international date-line switches to being west of it), the return shall be invalid. Passing an invalid time-zone as zone will also produce an invalid result, as shall dates that end outside the range representable by QDateTime .

另请参阅 startOfDay ().

`[since 6.5]` QDateTime QDate:: endOfDay () const

这是重载函数。

该函数在 Qt 6.5 引入。

`[static constexpr]` QDate QDate:: fromJulianDay ( qint64 jd )

Converts the Julian day jd 到 QDate .

另请参阅 toJulianDay ().

`[static constexpr noexcept, since 6.4]` QDate QDate:: fromStdSysDays (const std::chrono::sys_days & days )

返回 QDate days days after January 1st, 1970 (the UNIX epoch). If days is negative, the returned date will be before the epoch.

注意： This function requires C++20.

该函数在 Qt 6.4 引入。

另请参阅 toStdSysDays ().

`[static]` QDate QDate:: fromString (const QString & string , Qt::DateFormat format = Qt::TextDate)

返回 QDate 表示通过 string ，使用 format given, or an invalid date if the string cannot be parsed.

Note for Qt::TextDate : only English month names (e.g. "Jan" in short form or "January" in long form) are recognized.

另请参阅 toString () 和 QLocale::toDate ().

`[static, since 6.0]` QDate QDate:: fromString ( QStringView string , Qt::DateFormat format = Qt::TextDate)

这是重载函数。

该函数在 Qt 6.0 引入。

`[static, since 6.0]` QDate QDate:: fromString ( QStringView string , QStringView format , QCalendar cal )

这是重载函数。

该函数在 Qt 6.0 引入。

`[static, since 6.0]` QDate QDate:: fromString (const QString & string , QStringView format , QCalendar cal )

这是重载函数。

该函数在 Qt 6.0 引入。

`[static]` QDate QDate:: fromString (const QString & string , const QString & format , QCalendar cal )

这是重载函数。

`[static, since 6.7]` QDate QDate:: fromString ( QStringView string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

这是重载函数。

Uses a default-constructed QCalendar .

该函数在 Qt 6.7 引入。

`[static, since 6.7]` QDate QDate:: fromString ( QStringView string , QStringView format , int baseYear , QCalendar cal )

这是重载函数。

该函数在 Qt 6.7 引入。

`[static, since 6.7]` QDate QDate:: fromString (const QString & string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

这是重载函数。

Uses a default-constructed QCalendar .

该函数在 Qt 6.7 引入。

`[static, since 6.0]` QDate QDate:: fromString (const QString & string , QStringView format , int baseYear , QCalendar cal )

这是重载函数。

该函数在 Qt 6.0 引入。

`[static, since 6.7]` QDate QDate:: fromString (const QString & string , const QString & format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

这是重载函数。

Uses a default-constructed QCalendar .

该函数在 Qt 6.7 引入。

`[static]` QDate QDate:: fromString (const QString & string , const QString & format , int baseYear , QCalendar cal )

返回 QDate 表示通过 string ，使用 format given, or an invalid date if the string cannot be parsed.

Uses cal as calendar if supplied, else the Gregorian calendar. Ranges of values in the format descriptions below are for the latter; they may be different for other calendars.

These expressions may be used for the format:

表达式	输出
d	The day as a number without a leading zero (1 to 31)
dd	The day as a number with a leading zero (01 to 31)
ddd	The abbreviated day name ('Mon' to 'Sun').
dddd	The long day name ('Monday' to 'Sunday').
M	The month as a number without a leading zero (1 to 12)
MM	The month as a number with a leading zero (01 to 12)
MMM	The abbreviated month name ('Jan' to 'Dec').
MMMM	The long month name ('January' to 'December').
yy	The year as a two digit number (00 to 99)
yyyy	The year as a four digit number, possibly plus a leading minus sign for negative years.

注意： Day and month names must be given in English (C locale). If localized month and day names are to be recognized, use QLocale::system ().toDate().

All other input characters will be treated as text. Any non-empty sequence of characters enclosed in single quotes will also be treated (stripped of the quotes) as text and not be interpreted as expressions. 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 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:

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

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

Field	默认值
Year	baseYear (or 1900)
Month	1 (January)
Day	1

当 format only specifies the last two digits of a year, the 100 years starting at baseYear are the candidates first considered. Prior to 6.7 there was no baseYear parameter and 1900 was always used. This is the default for baseYear , selecting a year from then to 1999. Passing 1976 as baseYear will select a year from 1976 through 2075, for example. When the format also includes month, day (of month) and day-of-week, these suffice to imply the century. In such a case, a matching date is selected in the nearest century to the one indicated by baseYear , prefering later over earlier. See QCalendar::matchCenturyToWeekday () 和 Date ambiguities for further details,

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

注意： If a format character is repeated more times than the longest expression in the table above using it, this part of the format will be read as several expressions with no separator between them; the longest above, possibly repeated as many times as there are copies of it, ending with a residue that may be a shorter expression. Thus 'MMMMMMMMMM' would match "MayMay05" and set the month to May. Likewise, 'MMMMMM' would match "May08" and find it inconsistent, leading to an invalid date.

Date ambiguities

Different cultures use different formats for dates and, as a result, users may mix up the order in which date fields should be given. For example, "Wed 28-Nov-01" might mean either 2028 November 1st or the 28th of November, 2001 (each of which happens to be a Wednesday). Using format "ddd yy-MMM-dd" it shall be interpreted the first way, using "ddd dd-MMM-yy" the second. However, which the user meant may depend on the way the user normally writes dates, rather than the format the code was expecting.

The example considered above mixed up day of the month and a two-digit year. Similar confusion can arise over interchanging the month and day of the month, when both are given as numbers. In these cases, including a day of the week field in the date format can provide some redundancy, that may help to catch errors of this kind. However, as in the example above, this is not always effective: the interchange of two fields (or their meanings) may produce dates with the same day of the week.

Including a day of the week in the format can also resolve the century of a date specified using only the last two digits of its year. Unfortunately, when combined with a date in which the user (or other source of data) has mixed up two of the fields, this resolution can lead to finding a date which does match the format's reading but isn't the one intended by its author. Likewise, if the user simply gets the day of the week wrong, in an otherwise correct date, this can lead a date in a different century. In each case, finding a date in a different century can turn a wrongly-input date into a wildly different one.

The best way to avoid date ambiguities is to use four-digit years and months specified by name (whether full or abbreviated), ideally collected via user interface idioms that make abundantly clear to the user which part of the date they are selecting. Including a day of the week can also help by providing the means to check consistency of the data. Where data comes from the user, using a format supplied by a locale selected by the user, it is best to use a long format as short formats are more likely to use two-digit years. Of course, it is not always possible to control the format - data may come from a source you do not control, for example.

As a result of these possible sources of confusion, particularly when you cannot be sure an unambiguous format is in use, it is important to check that the result of reading a string as a date is not just valid but reasonable for the purpose for which it was supplied. If the result is outside some range of reasonable values, it may be worth getting the user to confirm their date selection, showing the date read from the string in a long format that does include month name and four-digit year, to make it easier for them to recognize any errors.

另请参阅 toString (), QDateTime::fromString (), QTime::fromString ()，和 QLocale::toDate ().

void QDate:: getDate ( int * year , int * month , int * day ) const

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

Returns 0 if the date is invalid.

注意： In Qt versions prior to 5.7, this function is marked as non- const .

另请参阅 year (), month (), day (), isValid ()，和 QCalendar::partsFromDate ().

`[static]` bool QDate:: isLeapYear ( int year )

返回 true if the specified year is a leap year in the Gregorian calendar; otherwise returns false .

另请参阅 QCalendar::isLeapYear ().

`[constexpr]` bool QDate:: isNull () const

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

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

另请参阅 isValid ().

`[constexpr]` bool QDate:: isValid () const

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

另请参阅 isNull () 和 QCalendar::isDateValid ().

`[static]` bool QDate:: isValid ( int year , int month , int day )

这是重载函数。

返回 true if the specified date ( year , month ，和 day ) is valid in the Gregorian calendar; otherwise returns false .

范例：

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)

另请参阅 isNull (), setDate ()，和 QCalendar::isDateValid ().

int QDate:: month ( QCalendar cal ) const

Returns the month-number for the date.

Numbers the months of the year starting with 1 for the first. Uses cal as calendar if supplied, else the Gregorian calendar, for which the month numbering is as follows:

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

Returns 0 if the date is invalid. Note that some calendars may have more than 12 months in some years.

另请参阅 year (), day ()，和 QCalendar::partsFromDate ().

int QDate:: month () const

这是重载函数。

bool QDate:: setDate ( int year , int month , int day )

Sets this to represent the date, in the Gregorian calendar, with the given year , month and day numbers. Returns true if the resulting date is valid, otherwise it sets this to represent an invalid date and returns false.

另请参阅 isValid () 和 QCalendar::dateFromParts ().

bool QDate:: setDate ( int year , int month , int day , QCalendar cal )

Sets this to represent the date, in the given calendar cal ，采用给定 year , month and day numbers. Returns true if the resulting date is valid, otherwise it sets this to represent an invalid date and returns false.

另请参阅 isValid () 和 QCalendar::dateFromParts ().

QDateTime QDate:: startOfDay (const QTimeZone & zone ) const

Returns the start-moment of the day.

When a day starts depends on a how time is described: each day starts and ends earlier for those in time-zones further west and later for those in time-zones further east. The time representation to use can be specified by an optional time zone . The default time representation is the system's local time.

Usually, the start of the day is midnight, 00:00: however, if a time-zone transition causes the given date to skip over that midnight (e.g. a DST spring-forward skipping over the first hour of the day day), the actual earliest time in the day is returned. This can only arise when the time representation is a time-zone or local time.

当 zone has a timeSpec() of is Qt::OffsetFromUTC or Qt::UTC , the time representation has no transitions so the start of the day is QTime (0, 0).

另请参阅 endOfDay ().

`[since 6.5]` QDateTime QDate:: startOfDay () const

这是重载函数。

该函数在 Qt 6.5 引入。

`[constexpr]` qint64 QDate:: toJulianDay () const

Converts the date to a Julian day.

另请参阅 fromJulianDay ().

`[constexpr noexcept]` std::chrono::sys_days QDate:: toStdSysDays () const

Returns the number of days between January 1st, 1970 (the UNIX epoch) and this date, represented as a std::chrono::sys_days object. If this date is before the epoch, the number of days will be negative.

注意： This function requires C++20.

另请参阅 fromStdSysDays () 和 daysTo ().

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

这是重载函数。

Returns the date as a string. The format 参数确定字符串的格式。

若 format is Qt::TextDate , the string is formatted in the default way. The day and month names will be in English. An example of this formatting is "Sat May 20 1995". For localized formatting, see QLocale::toString ().

若 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.

若 format is Qt::RFC2822Date , the string is formatted in an RFC 2822 compatible way. An example of this formatting is "20 May 1995".

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

警告： The Qt::ISODate format is only valid for years in the range 0 to 9999.

另请参阅 fromString () 和 QLocale::toString ().

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

这是重载函数。

QString QDate:: toString ( QStringView format ) const

这是重载函数。

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

Returns the ISO 8601 week number (1 to 53).

Returns 0 if the date is invalid. Otherwise, returns the week number for the date. If yearNumber 不是 nullptr (its default), stores the year as * yearNumber .

In accordance with ISO 8601, each week falls in the year to which most of its days belong, in the Gregorian calendar. As ISO 8601's week starts on Monday, this is the year in which the week's Thursday falls. Most years have 52 weeks, but some have 53.

注意： * 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.

另请参阅 isValid ().

int QDate:: year ( QCalendar cal ) const

返回此日期的年数。

Uses cal as calendar, if supplied, else the Gregorian calendar.

Returns 0 if the date is invalid. For some calendars, dates before their first year may all be invalid.

If using a calendar which has a year 0, check using isValid () if the return is 0. Such calendars use negative year numbers in the obvious way, with year 1 preceded by year 0, in turn preceded by year -1 and so on.

Some calendars, despite having no year 0, have a conventional numbering of the years before their first year, counting backwards from 1. For example, in the proleptic Gregorian calendar, successive years before 1 CE (the first year) are identified as 1 BCE, 2 BCE, 3 BCE and so on. For such calendars, negative year numbers are used to indicate these years before year 1, with -1 indicating the year before 1.

另请参阅 month (), day (), QCalendar::hasYearZero (), QCalendar::isProleptic ()，和 QCalendar::partsFromDate ().

int QDate:: year () const

这是重载函数。

QDate Class

公共函数

静态公共成员

相关非成员

详细描述

备注

有效日期范围

成员函数文档编制

[constexpr noexcept, since 6.4] QDate:: QDate ( std::chrono::year_month_day date )

[constexpr noexcept, since 6.4] QDate:: QDate ( std::chrono::year_month_day_last date )

[constexpr noexcept, since 6.4] QDate:: QDate ( std::chrono::year_month_weekday date )

[constexpr noexcept, since 6.4] QDate:: QDate ( std::chrono::year_month_weekday_last date )

QString QDate:: toString ( QStringView format , QCalendar cal ) const

QString QDate:: toString (const QString & format , QCalendar cal ) const

[constexpr] QDate:: QDate ()

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

QDate QDate:: addDays ( qint64 ndays ) const

[since 6.4] QDate QDate:: addDuration ( std::chrono::days ndays ) const

QDate QDate:: addMonths ( int nmonths , QCalendar cal ) const

QDate QDate:: addMonths ( int nmonths ) const

QDate QDate:: addYears ( int nyears , QCalendar cal ) const

QDate QDate:: addYears ( int nyears ) const

[static] QDate QDate:: currentDate ()

int QDate:: day ( QCalendar cal ) const

int QDate:: day () const

int QDate:: dayOfWeek ( QCalendar cal ) const

int QDate:: dayOfWeek () const

int QDate:: dayOfYear ( QCalendar cal ) const

int QDate:: dayOfYear () const

int QDate:: daysInMonth ( QCalendar cal ) const

int QDate:: daysInMonth () const

int QDate:: daysInYear ( QCalendar cal ) const

int QDate:: daysInYear () const

qint64 QDate:: daysTo ( QDate d ) const

QDateTime QDate:: endOfDay (const QTimeZone & zone ) const

[since 6.5] QDateTime QDate:: endOfDay () const

[static constexpr] QDate QDate:: fromJulianDay ( qint64 jd )

[static constexpr noexcept, since 6.4] QDate QDate:: fromStdSysDays (const std::chrono::sys_days & days )

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

[static, since 6.0] QDate QDate:: fromString ( QStringView string , Qt::DateFormat format = Qt::TextDate)

[static, since 6.0] QDate QDate:: fromString ( QStringView string , QStringView format , QCalendar cal )

[static, since 6.0] QDate QDate:: fromString (const QString & string , QStringView format , QCalendar cal )

[static] QDate QDate:: fromString (const QString & string , const QString & format , QCalendar cal )

[static, since 6.7] QDate QDate:: fromString ( QStringView string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

[static, since 6.7] QDate QDate:: fromString ( QStringView string , QStringView format , int baseYear , QCalendar cal )

[static, since 6.7] QDate QDate:: fromString (const QString & string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

[static, since 6.0] QDate QDate:: fromString (const QString & string , QStringView format , int baseYear , QCalendar cal )

[static, since 6.7] QDate QDate:: fromString (const QString & string , const QString & format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

[static] QDate QDate:: fromString (const QString & string , const QString & format , int baseYear , QCalendar cal )

Date ambiguities

void QDate:: getDate ( int * year , int * month , int * day ) const

[static] bool QDate:: isLeapYear ( int year )

[constexpr] bool QDate:: isNull () const

[constexpr] bool QDate:: isValid () const

[static] bool QDate:: isValid ( int year , int month , int day )

int QDate:: month ( QCalendar cal ) const

int QDate:: month () const

bool QDate:: setDate ( int year , int month , int day )

bool QDate:: setDate ( int year , int month , int day , QCalendar cal )

QDateTime QDate:: startOfDay (const QTimeZone & zone ) const

[since 6.5] QDateTime QDate:: startOfDay () const

[constexpr] qint64 QDate:: toJulianDay () const

[constexpr noexcept] std::chrono::sys_days QDate:: toStdSysDays () const

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

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

QString QDate:: toString ( QStringView format ) const

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

int QDate:: year ( QCalendar cal ) const

int QDate:: year () const

相关非成员

[constexpr noexcept] bool operator!= (const QDate & lhs , const QDate & rhs )

[constexpr noexcept] bool operator< (const QDate & lhs , const QDate & rhs )

QDataStream & operator<< ( QDataStream & out , QDate date )

[constexpr noexcept] bool operator<= (const QDate & lhs , const QDate & rhs )

[constexpr noexcept] bool operator== (const QDate & lhs , const QDate & rhs )

[constexpr noexcept] bool operator> (const QDate & lhs , const QDate & rhs )

[constexpr noexcept] bool operator>= (const QDate & lhs , const QDate & rhs )

QDataStream & operator>> ( QDataStream & in , QDate & date )

内容

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_day date )

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_day_last date )

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_weekday date )

`[constexpr noexcept, since 6.4]` QDate:: QDate ( std::chrono::year_month_weekday_last date )

`[constexpr]` QDate:: QDate ()

`[since 6.4]` QDate QDate:: addDuration ( std::chrono::days ndays ) const

`[static]` QDate QDate:: currentDate ()

`[since 6.5]` QDateTime QDate:: endOfDay () const

`[static constexpr]` QDate QDate:: fromJulianDay ( qint64 jd )

`[static constexpr noexcept, since 6.4]` QDate QDate:: fromStdSysDays (const std::chrono::sys_days & days )

`[static]` QDate QDate:: fromString (const QString & string , Qt::DateFormat format = Qt::TextDate)

`[static, since 6.0]` QDate QDate:: fromString ( QStringView string , Qt::DateFormat format = Qt::TextDate)

`[static, since 6.0]` QDate QDate:: fromString ( QStringView string , QStringView format , QCalendar cal )

`[static, since 6.0]` QDate QDate:: fromString (const QString & string , QStringView format , QCalendar cal )

`[static]` QDate QDate:: fromString (const QString & string , const QString & format , QCalendar cal )

`[static, since 6.7]` QDate QDate:: fromString ( QStringView string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

`[static, since 6.7]` QDate QDate:: fromString ( QStringView string , QStringView format , int baseYear , QCalendar cal )

`[static, since 6.7]` QDate QDate:: fromString (const QString & string , QStringView format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

`[static, since 6.0]` QDate QDate:: fromString (const QString & string , QStringView format , int baseYear , QCalendar cal )

`[static, since 6.7]` QDate QDate:: fromString (const QString & string , const QString & format , int baseYear = QLocale::DefaultTwoDigitBaseYear)

`[static]` QDate QDate:: fromString (const QString & string , const QString & format , int baseYear , QCalendar cal )

`[static]` bool QDate:: isLeapYear ( int year )

`[constexpr]` bool QDate:: isNull () const

`[constexpr]` bool QDate:: isValid () const

`[static]` bool QDate:: isValid ( int year , int month , int day )

`[since 6.5]` QDateTime QDate:: startOfDay () const

`[constexpr]` qint64 QDate:: toJulianDay () const

`[constexpr noexcept]` std::chrono::sys_days QDate:: toStdSysDays () const

`[constexpr noexcept]` bool operator!= (const QDate & lhs , const QDate & rhs )

`[constexpr noexcept]` bool operator< (const QDate & lhs , const QDate & rhs )

`[constexpr noexcept]` bool operator<= (const QDate & lhs , const QDate & rhs )

`[constexpr noexcept]` bool operator== (const QDate & lhs , const QDate & rhs )

`[constexpr noexcept]` bool operator> (const QDate & lhs , const QDate & rhs )

`[constexpr noexcept]` bool operator>= (const QDate & lhs , const QDate & rhs )