QDate Class

成员函数

QDate::QDate()

Constructs a null date. Null dates are invalid.

参见 isNull() and isValid().

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

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

If the specified date is invalid, the date is not set and isValid() returns false.

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

参见 isValid().

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.

参见 addMonths(), addYears(), and daysTo().

QDate QDate::addMonths(int nmonths) const

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

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.

参见 addDays() and addYears().

QDate QDate::addYears(int nyears) const

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

Note: If the ending day/month combination does not exist in the resulting year (i.e., if the date was Feb 29 and the final year is not a leap year), this function will return a date that is the latest valid date (that is, Feb 28).

参见 addDays() and addMonths().

[static] QDate QDate::currentDate()

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

参见 QTime::currentTime() and QDateTime::currentDateTime().

int QDate::day() const

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

Returns 0 if the date is invalid.

参见 year(), month(), dayOfWeek().

int QDate::dayOfWeek() const

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

Returns 0 if the date is invalid.

参见 day(), dayOfYear(), and Qt::DayOfWeek.

int QDate::dayOfYear() const

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

Returns 0 if the date is invalid.

参见 day() and dayOfWeek().

int QDate::daysInMonth() const

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

Returns 0 if the date is invalid.

参见 day() and daysInYear().

int QDate::daysInYear() const

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

Returns 0 if the date is invalid.

参见 day() and daysInMonth().

qint64 QDate::daysTo(const QDate &d) const

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

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

参见 addDays().

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

Converts the Julian day jd to a QDate.

参见 toJulianDay().

[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: It is recommended that you use the English short month names (e.g. "Jan"). Although localized month names can also be used, they depend on the user's locale settings.

参见 toString() and QLocale::toDate().

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

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

These expressions may be used for the format:

All other input characters will be treated as text. Any sequence of characters that are enclosed in single quotes will also be treated as text and will not be used as an expression. For example:

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

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

参见 toString(), QDateTime::fromString(), QTime::fromString(), and 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.

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

This function was introduced in Qt 4.5.

参见 year(), month(), day(), and isValid().

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

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

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().

参见 isValid().

bool QDate::isValid() const

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

参见 isNull().

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

This is an overloaded function.

Returns true if the specified date (year, month, and day) is valid; 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)

参见 isNull() and setDate().

[static] QString QDate::longDayName(int weekday, MonthNameType type = DateFormat)

Returns the long name of the weekday for the representation specified by type.

The days are enumerated using the following convention:

• 1 = "Monday"
• 2 = "Tuesday"
• 3 = "Wednesday"
• 4 = "Thursday"
• 5 = "Friday"
• 6 = "Saturday"
• 7 = "Sunday"

The day names will be localized according to the system's locale settings, i.e. using QLocale::system().

Returns an empty string if the date is invalid.

This function was introduced in Qt 4.5.

参见 toString(), shortDayName(), shortMonthName(), and longMonthName().

[static] QString QDate::longMonthName(int month, MonthNameType type = DateFormat)

Returns the long name of the month for the representation specified by type.

The months are enumerated using the following convention:

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

The month names will be localized according to the system's locale settings, i.e. using QLocale::system().

Returns an empty string if the date is invalid.

This function was introduced in Qt 4.5.

参见 toString(), shortMonthName(), shortDayName(), and longDayName().

int QDate::month() const

Returns the number corresponding to the month of this date, using the following convention:

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

Returns 0 if the date is invalid.

参见 year() and day().

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

Sets the date's year, month, and day. Returns true if the date is valid; otherwise returns false.

If the specified date is invalid, the QDate object is set to be invalid.

This function was introduced in Qt 4.2.

参见 isValid().

[static] QString QDate::shortDayName(int weekday, MonthNameType type = DateFormat)

Returns the short name of the weekday for the representation specified by type.

The days are enumerated using the following convention:

• 1 = "Mon"
• 2 = "Tue"
• 3 = "Wed"
• 4 = "Thu"
• 5 = "Fri"
• 6 = "Sat"
• 7 = "Sun"

The day names will be localized according to the system's locale settings, i.e. using QLocale::system().

Returns an empty string if the date is invalid.

This function was introduced in Qt 4.5.

参见 toString(), shortMonthName(), longMonthName(), and longDayName().

[static] QString QDate::shortMonthName(int month, MonthNameType type = DateFormat)

Returns the short name of the month for the representation specified by type.

The months are enumerated using the following convention:

• 1 = "Jan"
• 2 = "Feb"
• 3 = "Mar"
• 4 = "Apr"
• 5 = "May"
• 6 = "Jun"
• 7 = "Jul"
• 8 = "Aug"
• 9 = "Sep"
• 10 = "Oct"
• 11 = "Nov"
• 12 = "Dec"

The month names will be localized according to the system's locale settings, i.e. using QLocale::system().

Returns an empty string if the date is invalid.

This function was introduced in Qt 4.5.

参见 toString(), longMonthName(), shortDayName(), and longDayName().

qint64 QDate::toJulianDay() const

Converts the date to a Julian day.

参见 fromJulianDay().

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

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

These expressions may be used:

All other input characters will be ignored. Any sequence of characters that are enclosed in single quotes will be treated as text and not be used as an expression. Two consecutive single quotes ("''") are replaced by a singlequote in the output. Formats without separators (e.g. "ddMM") are currently not supported.

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

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

参见 fromString(), QDateTime::toString(), QTime::toString(), and QLocale::toString().

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

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. QDate::shortDayName() and QDate::shortMonthName() are used to generate the string, so the day and month names will be localized names using the system locale, i.e. QLocale::system(). An example of this formatting is "Sat May 20 1995".

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::SystemLocaleShortDate or Qt::SystemLocaleLongDate, the string format depends on the locale settings of the system. Identical to calling QLocale::system().toString(date, QLocale::ShortFormat) or QLocale::system().toString(date, QLocale::LongFormat).

If the format is Qt::DefaultLocaleShortDate or Qt::DefaultLocaleLongDate, the string format depends on the default application locale. This is the locale set with QLocale::setDefault(), or the system locale if no default locale has been set. Identical to calling QLocale().toString(date, QLocale::ShortFormat) or QLocale().toString(date, QLocale::LongFormat).

If the 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 restriction may apply to locale-aware formats as well, depending on the locale settings.

参见 fromString(), shortDayName(), shortMonthName(), and QLocale::toString().

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

Returns the week number (1 to 53), and stores the year in *yearNumber unless yearNumber is null (the default).

Returns 0 if the date is invalid.

In accordance with ISO 8601, weeks start on Monday and the first Thursday of a year is always in week 1 of that year. Most years have 52 weeks, but some have 53.

*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.

参见 isValid().

int QDate::year() const

Returns the year of this date. Negative numbers indicate years before 1 CE, such that year -44 is 44 BCE.

Returns 0 if the date is invalid.

参见 month() and day().

bool QDate::operator!=(const QDate &d) const

Returns true if this date is different from d; otherwise returns false.

bool QDate::operator<(const QDate &d) const

Returns true if this date is earlier than d; otherwise returns false.

bool QDate::operator<=(const QDate &d) const

Returns true if this date is earlier than or equal to d; otherwise returns false.

bool QDate::operator==(const QDate &d) const

Returns true if this date is equal to d; otherwise returns false.

bool QDate::operator>(const QDate &d) const

Returns true if this date is later than d; otherwise returns false.

bool QDate::operator>=(const QDate &d) const

Returns true if this date is later than or equal to d; otherwise returns false.