The QDate class provides date functions. 更多...
| 头： | #include <QDate> |
| qmake: | QT += core |
注意： 此类的所有函数 可重入 .
| enum | MonthNameType { DateFormat, StandaloneFormat } |
| QDate () | |
| QDate (int y , int m , int d ) | |
| QDate | addDays (qint64 ndays ) const |
| QDate | addMonths (int nmonths ) const |
| QDate | addYears (int nyears ) const |
| int | day () const |
| int | dayOfWeek () const |
| int | dayOfYear () const |
| int | daysInMonth () const |
| int | daysInYear () const |
| qint64 | daysTo (const QDate & d ) const |
| void | getDate (int * year , int * month , int * day ) const |
| bool | isNull () const |
| bool | isValid () const |
| int | month () const |
| bool | setDate (int year , int month , int day ) |
| qint64 | toJulianDay () const |
| QString | toString (const QString & format ) const |
| QString | toString (Qt::DateFormat format = Qt::TextDate) const |
| QString | toString (QStringView format ) const |
| int | weekNumber (int * yearNumber = nullptr) const |
| int | year () const |
| bool | operator!= (const QDate & d ) const |
| bool | operator< (const QDate & d ) const |
| bool | operator<= (const QDate & d ) const |
| bool | operator== (const QDate & d ) const |
| bool | operator> (const QDate & d ) const |
| bool | operator>= (const QDate & d ) const |
| QDate | currentDate () |
| QDate | fromJulianDay (qint64 jd ) |
| QDate | fromString (const QString & string , Qt::DateFormat format = Qt::TextDate) |
| QDate | fromString (const QString & string , const QString & format ) |
| bool | isLeapYear (int year ) |
| bool | isValid (int year , int month , int day ) |
| QDataStream & | operator<< (QDataStream & out , const QDate & date ) |
| QDataStream & | operator>> (QDataStream & in , QDate & date ) |
The QDate class provides date functions.
A QDate object represents a particular date. This can be expressed as a calendar date, i.e. year, month, and day numbers, in the proleptic Gregorian calendar.
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 () 函数返回 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. Also, dayOfWeek () 和 dayOfYear () functions are provided. The same information is provided in textual format by toString (). The day and month numbers can be mapped to names using QLocal.
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.
There is no year 0. Dates in that year are considered invalid. The year -1 is the year "1 before Christ" or "1 before current era." The day before 1 January 1 CE, QDate (1, 1, 1), is 31 December 1 BCE, QDate (-1, 12, 31).
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 dates able to be stored by QDate as a Julian Day number is for technical reasons limited to between -784350574879 and 784354017364, which means from before 2 billion BCE to after 2 billion CE.
另请参阅 QTime , QDateTime , QDateEdit , QDateTimeEdit ，和 QCalendarWidget .
This enum describes the types of the string representation used for the month name.
| 常量 | 值 | 描述 |
|---|---|---|
QDate::DateFormat
|
0
|
This type of name can be used for date-to-string formatting. |
QDate::StandaloneFormat
|
1
|
This type is used when you need to enumerate months or weekdays. Usually standalone names are represented in singular forms with capitalized first letter. |
该枚举在 Qt 4.5 引入或被修改。
Returns the date as a string. The format 参数确定结果字符串的格式。
这些表达式可以使用：
| 表达式 | 输出 |
|---|---|
| d | the day as number without a leading zero (1 to 31) |
| dd | the day as number with a leading zero (01 to 31) |
| ddd | the abbreviated localized day name (e.g. 'Mon' to 'Sun'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| dddd | the long localized day name (e.g. 'Monday' to 'Sunday'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| M | the month as number without a leading zero (1 to 12) |
| MM | the month as number with a leading zero (01 to 12) |
| MMM | the abbreviated localized month name (e.g. 'Jan' to 'Dec'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| MMMM | the long localized month name (e.g. 'January' to 'December'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| yy | the year as two digit number (00 to 99) |
| yyyy | the year as four digit number. If the year is negative, a minus sign is prepended in addition. |
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。
另请参阅 fromString (), QDateTime::toString (), QTime::toString ()，和 QLocale::toString ().
Constructs a null date. Null dates are invalid.
Constructs a date with year y , month m and day d .
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 ().
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 ().
返回 QDate object containing a date nmonths later than the date of this object (or earlier if nmonths is negative).
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.
另请参阅 addDays () 和 addYears ().
返回 QDate object containing a date nyears later than the date of this object (or earlier if nyears is negative).
注意： 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).
另请参阅 addDays () 和 addMonths ().
[static]
QDate
QDate::
currentDate
()
Returns the current date, as reported by the system clock.
另请参阅 QTime::currentTime () 和 QDateTime::currentDateTime ().
Returns the day of the month (1 to 31) of this date.
Returns 0 if the date is invalid.
另请参阅 year (), month ()，和 dayOfWeek ().
Returns the weekday (1 = Monday to 7 = Sunday) for this date.
Returns 0 if the date is invalid.
另请参阅 day (), dayOfYear ()，和 Qt::DayOfWeek .
Returns the day of the year (1 to 365 or 366 on leap years) for this date.
Returns 0 if the date is invalid.
Returns the number of days in the month (28 to 31) for this date.
Returns 0 if the date is invalid.
另请参阅 day () 和 daysInYear ().
Returns the number of days in the year (365 or 366) for this date.
Returns 0 if the date is invalid.
另请参阅 day () 和 daysInMonth ().
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 ().
[static]
QDate
QDate::
fromJulianDay
(
qint64
jd
)
Converts the Julian day jd 到 QDate .
另请参阅 toJulianDay ().
[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 : 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.
另请参阅 toString () 和 QLocale::toDate ().
[static]
QDate
QDate::
fromString
(const
QString
&
string
, const
QString
&
format
)
返回 QDate 表示通过 string ，使用 format given, or an invalid date if the string cannot be parsed.
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 localized day name (e.g. 'Mon' to 'Sun'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| dddd | The long localized day name (e.g. 'Monday' to 'Sunday'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| 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 localized month name (e.g. 'Jan' to 'Dec'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| MMMM | The long localized month name (e.g. 'January' to 'December'). Uses the system locale to localize the name, i.e. QLocale::system (). |
| yy | The year as two digit number (00 to 99) |
| yyyy | The year as four digit number. If the year is negative, a minus sign is prepended in addition. |
All other input characters will be treated as text. Any sequence of characters that are enclosed in single quotes will also be treated as text and will not be used as an expression. For example:
QDate date = QDate::fromString("1MM12car2003", "d'MM'MMcaryyyy"); // date is 1 December 2003
If the format is not satisfied, an invalid QDate is returned. The expressions that 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 | 1900 |
| Month | 1 |
| Day | 1 |
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
另请参阅 toString (), QDateTime::fromString (), QTime::fromString ()，和 QLocale::toDate ().
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
.
该函数在 Qt 4.5 引入。
另请参阅 year (), month (), day ()，和 isValid ().
[static]
bool
QDate::
isLeapYear
(
int
year
)
返回
true
if the specified
year
is a leap year; otherwise returns
false
.
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 ().
返回
true
if this date is valid; otherwise returns
false
.
另请参阅 isNull ().
[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; 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)
Returns the number corresponding to the month of this date, using the following convention:
Returns 0 if the date is invalid.
Sets the date's
year
,
month
，和
day
。返回
true
if the date is valid; otherwise returns
false
.
If the specified date is invalid, the QDate object is set to be invalid.
该函数在 Qt 4.2 引入。
另请参阅 isValid ().
Converts the date to a Julian day.
另请参阅 fromJulianDay ().
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 localized names using the system locale, i.e. QLocale::system (). An example of this formatting is "Sat May 20 1995".
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::SystemLocaleShortDate or Qt::SystemLocaleLongDate , the string format depends on the locale settings of the system. Identical to calling QLocale::system (). toString (date, QLocale::ShortFormat ) 或 QLocale::system (). toString (date, QLocale::LongFormat ).
若 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) .
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. This restriction may apply to locale-aware formats as well, depending on the locale settings.
另请参阅 fromString () 和 QLocale::toString ().
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.
另请参阅 isValid ().
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.
返回
true
if this date is different from
d
；否则返回
false
.
返回
true
若此日期早于
d
；否则返回 false。
返回
true
if this date is earlier than or equal to
d
；否则返回
false
.
返回
true
if this date is equal to
d
；否则返回 false。
返回
true
if this date is later than
d
；否则返回 false。
返回
true
if this date is later than or equal to
d
；否则返回
false
.
写入 date 到流 out .
另请参阅 序列化 Qt 数据类型 .
Reads a date from stream in 到 date .
另请参阅 序列化 Qt 数据类型 .