QDate Class

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▲

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

[since 6.4] QDate::QDate(int ymd)

[since 6.4] QDate::QDate(int ymd)

[since 6.4] QDate::QDate(int ymd)

Constructs a QDate representing the same date as ymd. 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];

This function was introduced in Qt 6.4.

[since 5.14] QDateTime QDate::startOfDay(const QTimeZone &zone) const

Returns the start-moment of the day. Usually, this shall be midnight at the start of the day: however, if a time-zone transition causes the given date to skip over that midnight (e.g. a DST spring-forward skipping from the end of the previous day to 01:00 of the new day), the actual earliest time in the day is returned. This can only arise when the start-moment is specified in terms of a time-zone (by passing its QTimeZone as zone) or in terms of local time (by passing Qt::LocalTime as spec; this is its default).

The offsetSeconds is ignored unless spec is Qt::OffsetFromUTC, when it gives the implied zone's offset from UTC. As UTC and such zones have no transitions, the start of the day is QTime(0, 0) in these cases.

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 Qt::TimeZone as spec (instead of passing a QTimeZone) or passing an invalid time-zone as zone will also produce an invalid result, as shall dates that start outside the range representable by QDateTime.

This function was introduced in Qt 5.14.

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[since 5.14] QDateTime QDate::endOfDay(const QTimeZone &zone) const

Returns the end-moment of the day. Usually, this is one millisecond before the midnight at the end of the day: however, if a time-zone transition causes the given date to skip over that midnight (e.g. a DST spring-forward skipping from just before 23:00 to the start of the next day), the actual latest time in the day is returned. This can only arise when the start-moment is specified in terms of a time-zone (by passing its QTimeZone as zone) or in terms of local time (by passing Qt::LocalTime as spec; this is its default).

The offsetSeconds is ignored unless spec is Qt::OffsetFromUTC, when it gives the implied zone's offset from UTC. As UTC and such zones have no transitions, the end of the day is QTime(23, 59, 59, 999) in these cases.

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 Qt::TimeZone as spec (instead of passing a QTimeZone) will also produce an invalid result, as shall dates that end outside the range representable by QDateTime.

This function was introduced in Qt 5.14.

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

These expressions may be used:

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):

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

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Constructs a null date. Null dates are invalid.

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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.

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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.

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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.

This function was introduced in Qt 6.4.

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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.

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This is an overloaded function.

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.

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This is an overloaded function.

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

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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.

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This is an overloaded function.

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.

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This is an overloaded function.

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.

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This is an overloaded function.

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.

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This is an overloaded function.

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.

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This is an overloaded function.

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

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Converts the Julian day jd to a QDate.

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

This function was introduced in Qt 6.4.

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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.

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This is an overloaded function.

This function was introduced in Qt 6.0.

This is an overloaded function.

This function was introduced in Qt 6.0.

This is an overloaded function.

This function was introduced in Qt 6.0.

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:

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:

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

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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.

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

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

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

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This is an overloaded function.

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)

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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.

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This is an overloaded function.

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.

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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.

This function was introduced in Qt 5.14.

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Converts the date to a Julian day.

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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.

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This is an overloaded function.

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.

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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.

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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.

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This is an overloaded function.

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

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

Writes the date to stream out.

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

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

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

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

Reads a date from stream in into the date.

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