- Qt 6.10
- Qt Core
- C++ Classes
- QDate
- Qt 6.10.2 Reference Documentation

# QDate Class

The QDate class provides date functions. More...

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

- List of all members, including inherited members
- Deprecated members

This class is strongly comparable.

This class is strongly comparable 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.

Note: All functions in this class are reentrant.

## Public Functions

| QDate()
`(since 6.4)` | QDate(std::chrono::year_month_day date)
`(since 6.4)` | QDate(std::chrono::year_month_day_last date)
`(since 6.4)` | QDate(std::chrono::year_month_weekday date)
`(since 6.4)` | QDate(std::chrono::year_month_weekday_last date)
| QDate(int y, int m, int d)
QDate | addDays(qint64 ndays) const
`(since 6.4)` 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
`(since 6.5)` 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
`(since 6.5)` QDateTime | startOfDay() const
qint64 | toJulianDay() const
std::chrono::sys_days | toStdSysDays() const
QString | toString(QStringView format, QCalendar cal) const
QString | toString(const QString &format, QCalendar cal) const
QString | toString(QStringView format) const
QString | toString(Qt::DateFormat format = Qt::TextDate) const
QString | toString(const QString &format) const
int | weekNumber(int *yearNumber = nullptr) const
int | year(QCalendar cal) const
int | year() const

## Static Public Members

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

## Related Non-Members

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)

## Detailed Description

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(). 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. 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() and 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() 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. QCalendar can also supply this information, in some cases more conveniently.

### Remarks

Note: 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().

#### Range of Valid Dates

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.

See also QTime, QDateTime, QCalendar, QDateTime::YearRange, QDateEdit, QDateTimeEdit, and QCalendarWidget.

## Member Function Documentation

### `[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)

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

For example:

     // 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];

Note: Unlike 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.

Note: This function requires C++20.

These functions were introduced in Qt 6.4.

### 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:

Expression | Output
--- | ---
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).

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

Format | Result
--- | ---
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.

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

Note: 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.

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

### `[constexpr]` 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.

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

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

See also isValid() and QCalendar::dateFromParts().

### QDate QDate::addDays(qint64 ndays) const

Returns a 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.

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

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

Returns a 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.

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

Note: This function requires C++20.

This function was introduced in Qt 6.4.

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

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

Returns a 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.

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 in the selected month.

See also addDays() and addYears().

### QDate QDate::addMonths(int nmonths) const

This is an overloaded function.

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

Returns a 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.

Note: 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).

See also addDays() and addMonths().

### QDate QDate::addYears(int nyears) const

This is an overloaded function.

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

Returns the system clock's current date.

See also QTime::currentTime() and 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.

See also year(), month(), dayOfWeek(), and QCalendar::partsFromDate().

### int QDate::day() const

This is an overloaded function.

### 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.

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

### int QDate::dayOfWeek() const

This is an overloaded function.

### 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.

See also day(), dayOfWeek(), and QCalendar::daysInYear().

### int QDate::dayOfYear() const

This is an overloaded function.

### 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.

See also day(), daysInYear(), QCalendar::daysInMonth(), QCalendar::maximumDaysInMonth(), and QCalendar::minimumDaysInMonth().

### int QDate::daysInMonth() const

This is an overloaded function.

### 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.

See also day(), daysInMonth(), QCalendar::daysInYear(), and QCalendar::maximumMonthsInYear().

### int QDate::daysInYear() const

This is an overloaded function.

### 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.

Example:

     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().

### 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.

When 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.

See also startOfDay().

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

This is an overloaded function.

This function was introduced in Qt 6.5.

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

Converts the Julian day jd to a QDate.

See also toJulianDay().

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

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

Note: This function requires C++20.

This function was introduced in Qt 6.4.

See also toStdSysDays().

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

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

See also toString() and QLocale::toDate().

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

Returns the QDate represented by the string, using the 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:

Expression | Output
--- | ---
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.

Note: 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 | Default value
--- | ---
Year | baseYear (or 1900)
Month | 1 (January)
Day | 1

When 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() and 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

Note: 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.

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

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

This is an overloaded function.

This function was introduced in Qt 6.0.

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

This is an overloaded function.

This function was introduced in Qt 6.0.

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

Uses a default-constructed QCalendar.

This is an overloaded function.

This function was introduced in Qt 6.7.

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

This is an overloaded function.

This function was introduced in Qt 6.0.

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

Uses a default-constructed QCalendar.

This is an overloaded function.

This function was introduced in Qt 6.7.

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

This is an overloaded function.

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

Uses a default-constructed QCalendar.

This is an overloaded function.

This function was introduced in Qt 6.7.

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

This is an overloaded function.

This function was introduced in Qt 6.7.

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

This is an overloaded function.

This function was introduced in Qt 6.0.

### 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.

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

See also year(), month(), day(), isValid(), and QCalendar::partsFromDate().

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

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

See also QCalendar::isLeapYear().

### `[constexpr]` bool QDate::isNull() 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().

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

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

See also isNull() and QCalendar::isDateValid().

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

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

Example:

     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)

This is an overloaded function.

See also isNull(), setDate(), and 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.

See also year(), day(), and QCalendar::partsFromDate().

### int QDate::month() const

This is an overloaded function.

### 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.

See also isValid() and QCalendar::dateFromParts().

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

Sets this to represent the date, in the given calendar cal, 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.

See also isValid() and 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.

When 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).

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 start outside the range representable by QDateTime.

See also endOfDay().

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

This is an overloaded function.

This function was introduced in Qt 6.5.

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

Converts the date to a Julian day.

See also 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.

Note: This function requires C++20.

See also fromStdSysDays() and daysTo().

### QString QDate::toString(QStringView format) const

This is an overloaded function.

### 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. 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().

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::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.

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

This is an overloaded function.

See also fromString() and QLocale::toString().

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

This is an overloaded function.

### 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 is not `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.

Note: *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(QCalendar cal) const

Returns the year of this date.

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.

See also month(), day(), QCalendar::hasYearZero(), QCalendar::isProleptic(), and QCalendar::partsFromDate().

### int QDate::year() const

This is an overloaded function.

## Related Non-Members

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

Returns `true` if lhs and rhs represent distinct days; otherwise returns `false`.

See also operator==().

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

Returns `true` if lhs is earlier than rhs; otherwise returns `false`.

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

Writes the date to stream out.

See also Serializing Qt Data Types.

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

Returns `true` if lhs is earlier than or equal to rhs; otherwise returns `false`.

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

Returns `true` if lhs and rhs represent the same day, otherwise `false`.

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

Returns `true` if lhs is later than rhs; otherwise returns `false`.

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

Returns `true` if lhs is later than or equal to rhs; otherwise returns `false`.

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

Reads a date from stream in into the date.

See also Serializing Qt Data Types.