QDateTime 类提供日期和时间功能。 更多...
| 头： | #include <QDateTime> |
| qmake: | QT += core |
注意： 此类的所有函数 可重入 .
| enum class | YearRange { First, Last } |
| QDateTime (QDateTime && other ) | |
| QDateTime (const QDateTime & other ) | |
| QDateTime (const QDate & date , const QTime & time , const QTimeZone & timeZone ) | |
| QDateTime (const QDate & date , const QTime & time , Qt::TimeSpec spec , int offsetSeconds ) | |
| QDateTime (const QDate & date , const QTime & time , Qt::TimeSpec spec = Qt::LocalTime) | |
| QDateTime (const QDate & date ) | |
| QDateTime () | |
| QDateTime & | operator= (const QDateTime & other ) |
| ~QDateTime () | |
| QDateTime | addDays (qint64 ndays ) const |
| QDateTime | addMSecs (qint64 msecs ) const |
| QDateTime | addMonths (int nmonths ) const |
| QDateTime | addSecs (qint64 s ) const |
| QDateTime | addYears (int nyears ) const |
| QDate | date () const |
| qint64 | daysTo (const QDateTime & other ) const |
| bool | isDaylightTime () const |
| bool | isNull () const |
| bool | isValid () const |
| qint64 | msecsTo (const QDateTime & other ) const |
| int | offsetFromUtc () const |
| qint64 | secsTo (const QDateTime & other ) const |
| void | setDate (const QDate & date ) |
| void | setMSecsSinceEpoch (qint64 msecs ) |
| void | setOffsetFromUtc (int offsetSeconds ) |
| void | setSecsSinceEpoch (qint64 secs ) |
| void | setTime (const QTime & time ) |
| void | setTimeSpec (Qt::TimeSpec spec ) |
| void | setTimeZone (const QTimeZone & toZone ) |
| void | swap (QDateTime & other ) |
| QTime | time () const |
| Qt::TimeSpec | timeSpec () const |
| QTimeZone | timeZone () const |
| QString | timeZoneAbbreviation () const |
| CFDateRef | toCFDate () const |
| QDateTime | toLocalTime () const |
| qint64 | toMSecsSinceEpoch () const |
| NSDate * | toNSDate () const |
| QDateTime | toOffsetFromUtc (int offsetSeconds ) const |
| qint64 | toSecsSinceEpoch () const |
| QString | toString (const QString & format ) const |
| QString | toString (Qt::DateFormat format = Qt::TextDate) const |
| QString | toString (const QString & format , QCalendar cal ) const |
| QString | toString (QStringView format ) const |
| QString | toString (QStringView format , QCalendar cal ) const |
| QDateTime | toTimeSpec (Qt::TimeSpec spec ) const |
| QDateTime | toTimeZone (const QTimeZone & timeZone ) const |
| QDateTime | toUTC () const |
| bool | operator!= (const QDateTime & other ) const |
| bool | operator< (const QDateTime & other ) const |
| bool | operator<= (const QDateTime & other ) const |
| bool | operator== (const QDateTime & other ) const |
| bool | operator> (const QDateTime & other ) const |
| bool | operator>= (const QDateTime & other ) const |
| QDateTime | currentDateTime () |
| QDateTime | currentDateTimeUtc () |
| qint64 | currentMSecsSinceEpoch () |
| qint64 | currentSecsSinceEpoch () |
| QDateTime | fromCFDate (CFDateRef date ) |
| QDateTime | fromMSecsSinceEpoch (qint64 msecs ) |
| QDateTime | fromMSecsSinceEpoch (qint64 msecs , Qt::TimeSpec spec , int offsetSeconds = 0) |
| QDateTime | fromMSecsSinceEpoch (qint64 msecs , const QTimeZone & timeZone ) |
| QDateTime | fromNSDate (const NSDate * date ) |
| QDateTime | fromSecsSinceEpoch (qint64 secs , Qt::TimeSpec spec = Qt::LocalTime, int offsetSeconds = 0) |
| QDateTime | fromSecsSinceEpoch (qint64 secs , const QTimeZone & timeZone ) |
| QDateTime | fromString (const QString & string , Qt::DateFormat format = Qt::TextDate) |
| QDateTime | fromString (const QString & string , const QString & format , QCalendar cal ) |
| QDataStream & | operator<< (QDataStream & out , const QDateTime & dateTime ) |
| QDataStream & | operator>> (QDataStream & in , QDateTime & dateTime ) |
A QDateTime object encodes a calendar date and a clock time (a "datetime"). It combines features of the QDate and QTime classes. It can read the current datetime from the system clock. It provides functions for comparing datetimes and for manipulating a datetime by adding a number of seconds, days, months, or years.
QDateTime can describe datetimes with respect to local time ，到 UTC , to a specified offset from UTC or to a specified time zone , in conjunction with the QTimeZone class. For example, a time zone of "Europe/Berlin" will apply the daylight-saving rules as used in Germany since 1970. In contrast, an offset from UTC of +3600 seconds is one hour ahead of UTC (usually written in ISO standard notation as "UTC+01:00"), with no daylight-saving offset or changes. When using either local time or a specified time zone, time-zone transitions such as the starts and ends of daylight-saving time (DST; but see below) are taken into account. The choice of system used to represent a datetime is described as its "timespec".
A QDateTime object is typically created either by giving a date and time explicitly in the constructor, or by using a static function such as currentDateTime () 或 fromMSecsSinceEpoch (). The date and time can be changed with setDate () 和 setTime (). A datetime can also be set using the setMSecsSinceEpoch () function that takes the time, in milliseconds, since 00:00:00 on January 1, 1970. The fromString () function returns a QDateTime, given a string and a date format used to interpret the date within the string.
QDateTime::currentDateTime () returns a QDateTime that expresses the current time with respect to local time. QDateTime::currentDateTimeUtc () returns a QDateTime that expresses the current time with respect to UTC.
date () 和 time () functions provide access to the date and time parts of the datetime. The same information is provided in textual format by the toString () 函数。
QDateTime provides a full set of operators to compare two QDateTime objects, where smaller means earlier and larger means later.
You can increment (or decrement) a datetime by a given number of milliseconds using addMSecs (), seconds using addSecs (), or days using addDays (). Similarly, you can use addMonths () 和 addYears ()。 daysTo () function returns the number of days between two datetimes, secsTo () returns the number of seconds between two datetimes, and msecsTo () returns the number of milliseconds between two datetimes. These operations are aware of daylight-saving time (DST) and other time-zone transitions, where applicable.
使用 toTimeSpec () to express a datetime in local time or UTC, toOffsetFromUtc () to express in terms of an offset from UTC, or toTimeZone () to express it with respect to a general time zone. You can use timeSpec () to find out what time-spec a QDateTime object stores its time relative to. When that is Qt::TimeZone , you can use timeZone () to find out which zone it is using.
注意： QDateTime does not account for leap seconds.
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 is 31 December 1 BCE.
The range of values that QDateTime can represent is dependent on the internal storage implementation. QDateTime is currently stored in a qint64 as a serial msecs value encoding the date and time. This restricts the date range to about +/- 292 million years, compared to the QDate range of +/- 2 billion years. Care must be taken when creating a QDateTime with extreme values that you do not overflow the storage. The exact range of supported values varies depending on the Qt::TimeSpec and time zone.
QDateTime uses the system's time zone information to determine the current local time zone and its offset from UTC. If the system is not configured correctly or not up-to-date, QDateTime will give wrong results.
QDateTime likewise uses system-provided information to determine the offsets of other timezones from UTC. If this information is incomplete or out of date, QDateTime will give wrong results. See the QTimeZone 文档编制了解更多细节。
On modern Unix systems, this means QDateTime usually has accurate information about historical transitions (including DST, see below) whenever possible. On Windows, where the system doesn't support historical timezone data, historical accuracy is not maintained with respect to timezone transitions, notably including DST.
QDateTime takes into account transitions between Standard Time and Daylight-Saving Time. For example, if the transition is at 2am and the clock goes forward to 3am, then there is a "missing" hour from 02:00:00 to 02:59:59.999 which QDateTime considers to be invalid. Any date arithmetic performed will take this missing hour into account and return a valid result. For example, adding one minute to 01:59:59 will get 03:00:00.
The range of valid dates taking DST into account is 1970-01-01 to the present, and rules are in place for handling DST correctly until 2037-12-31, but these could change. For dates after 2037, QDateTime makes a best guess using the rules for year 2037, but we can't guarantee accuracy; indeed, for any future date, the time-zone may change its rules before that date comes around. For dates before 1970, QDateTime doesn't take DST changes into account, even if the system's time zone database provides that information, although it does take into account changes to the time-zone's standard offset, where this information is available.
There is no explicit size restriction on an offset from UTC, but there is an implicit limit imposed when using the toString () 和 fromString () methods which use a [+|-]hh:mm format, effectively limiting the range to +/- 99 hours and 59 minutes and whole minutes only. Note that currently no time zone lies outside the range of +/- 14 hours.
另请参阅 QDate , QTime , QDateTimeEdit ，和 QTimeZone .
This enumerated type describes the range of years (in the Gregorian calendar) representable by QDateTime :
| 常量 | 值 | 描述 |
|---|---|---|
QDateTime::YearRange::First
|
-292275056
|
The later parts of this year are representable |
QDateTime::YearRange::Last
|
+292278994
|
The earlier parts of this year are representable |
All dates strictly between these two years are also representable. Note, however, that the Gregorian Calendar has no year zero.
注意： QDate can describe dates in a wider range of years. For most purposes, this makes little difference, as the range of years that QDateTime can support reaches 292 million years either side of 1970.
该枚举在 Qt 5.14 引入或被修改。
以字符串形式返回 datetime。 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. See QTime::toString () 和 QDate::toString () for the supported specifiers for time and date, respectively.
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 (assumed that the QDateTime is 21 May 2001 14:13:09.120):
| 格式 | 结果 |
|---|---|
| dd.MM.yyyy | 21.05.2001 |
| ddd MMMM d yy | Tue May 21 01 |
| hh:mm:ss.zzz | 14:13:09.120 |
| hh:mm:ss.z | 14:13:09.12 |
| h:m:s ap | 2:13:9 pm |
If the datetime is invalid, an empty string will be returned.
注意： If localized month and day names are desired, please switch to using QLocale::system (). toString () 作为 QDateTime methods shall change to use English (C locale) names at Qt 6.
另请参阅 fromString (), QDate::toString (), QTime::toString ()，和 QLocale::toString ().
Moves the content of the temporary other datetime to this object and leaves other in an unspecified (but proper) state.
该函数在 Qt 5.8 引入。
构造副本为 other datetime.
Constructs a datetime with the given date and time , using the Time Zone specified by timeZone .
若 date 有效和 time is not, the time will be set to 00:00:00.
若 timeZone is invalid then the datetime will be invalid.
该函数在 Qt 5.2 引入。
Constructs a datetime with the given date and time , using the time specification defined by spec and offsetSeconds 秒。
若 date 有效和 time is not, the time will be set to midnight.
若 spec 不是 Qt::OffsetFromUTC then offsetSeconds 将被忽略。
若 spec is Qt::OffsetFromUTC and offsetSeconds is 0 then the timeSpec () will be set to Qt::UTC , i.e. an offset of 0 seconds.
若 spec is Qt::TimeZone then the spec will be set to Qt::LocalTime , i.e. the current system time zone. To create a Qt::TimeZone datetime use the correct constructor.
该函数在 Qt 5.2 引入。
Constructs a datetime with the given date and time , using the time specification defined by spec .
若 date 有效和 time is not, the time will be set to midnight.
若 spec is Qt::OffsetFromUTC then it will be set to Qt::UTC , i.e. an offset of 0 seconds. To create a Qt::OffsetFromUTC datetime use the correct constructor.
若 spec is Qt::TimeZone then the spec will be set to Qt::LocalTime , i.e. the current system time zone. To create a Qt::TimeZone datetime use the correct constructor.
Constructs a datetime with the given date ，使用 Qt::LocalTime 作为 timeSpec () and the time at the start of that date.
另请参阅 QDate::startOfDay ().
Constructs a null datetime (i.e. null date and null time). A null datetime is invalid, since the date is invalid.
另请参阅 isValid ().
Makes a copy of the other datetime and returns a reference to the copy.
Destroys the datetime.
返回 QDateTime object containing a datetime ndays days later than the datetime of this object (or earlier if ndays is negative).
若 timeSpec () 是 Qt::LocalTime and the resulting date and time fall in the Standard Time to Daylight-Saving Time transition hour then the result will be adjusted accordingly, i.e. if the transition is at 2am and the clock goes forward to 3am and the result falls between 2am and 3am then the result will be adjusted to fall after 3am.
另请参阅 daysTo (), addMonths (), addYears ()，和 addSecs ().
返回 QDateTime object containing a datetime msecs miliseconds later than the datetime of this object (or earlier if msecs is negative).
If this datetime is invalid, an invalid datetime will be returned.
另请参阅 addSecs (), msecsTo (), addDays (), addMonths ()，和 addYears ().
返回 QDateTime object containing a datetime nmonths months later than the datetime of this object (or earlier if nmonths is negative).
若 timeSpec () 是 Qt::LocalTime and the resulting date and time fall in the Standard Time to Daylight-Saving Time transition hour then the result will be adjusted accordingly, i.e. if the transition is at 2am and the clock goes forward to 3am and the result falls between 2am and 3am then the result will be adjusted to fall after 3am.
另请参阅 daysTo (), addDays (), addYears ()，和 addSecs ().
返回 QDateTime object containing a datetime s seconds later than the datetime of this object (or earlier if s is negative).
If this datetime is invalid, an invalid datetime will be returned.
另请参阅 addMSecs (), secsTo (), addDays (), addMonths ()，和 addYears ().
返回 QDateTime object containing a datetime nyears years later than the datetime of this object (or earlier if nyears is negative).
若 timeSpec () 是 Qt::LocalTime and the resulting date and time fall in the Standard Time to Daylight-Saving Time transition hour then the result will be adjusted accordingly, i.e. if the transition is at 2am and the clock goes forward to 3am and the result falls between 2am and 3am then the result will be adjusted to fall after 3am.
另请参阅 daysTo (), addDays (), addMonths ()，和 addSecs ().
[static]
QDateTime
QDateTime::
currentDateTime
()
返回在本地时区由系统时钟报告的当前 datetime。
另请参阅 currentDateTimeUtc (), QDate::currentDate (), QTime::currentTime ()，和 toTimeSpec ().
[static]
QDateTime
QDateTime::
currentDateTimeUtc
()
Returns the current datetime, as reported by the system clock, in UTC.
该函数在 Qt 4.7 引入。
另请参阅 currentDateTime (), QDate::currentDate (), QTime::currentTime ()，和 toTimeSpec ().
[static]
qint64
QDateTime::
currentMSecsSinceEpoch
()
Returns the number of milliseconds since 1970-01-01T00:00:00 Universal Coordinated Time. This number is like the POSIX time_t variable, but expressed in milliseconds instead.
该函数在 Qt 4.7 引入。
另请参阅 currentDateTime (), currentDateTimeUtc (), toTime_t ()，和 toTimeSpec ().
[static]
qint64
QDateTime::
currentSecsSinceEpoch
()
Returns the number of seconds since 1970-01-01T00:00:00 Universal Coordinated Time.
该函数在 Qt 5.8 引入。
另请参阅 currentMSecsSinceEpoch ().
返回 datetime 的日期部分。
另请参阅 setDate (), time ()，和 timeSpec ().
Returns the number of days from this datetime to the other datetime. The number of days is counted as the number of times midnight is reached between this datetime to the other datetime. This means that a 10 minute difference from 23:55 to 0:05 the next day counts as one day.
若 other datetime is earlier than this datetime, the value returned is negative.
范例：
QDateTime startDate(QDate(2012, 7, 6), QTime(8, 30, 0)); QDateTime endDate(QDate(2012, 7, 7), QTime(16, 30, 0)); qDebug() << "Days from startDate to endDate: " << startDate.daysTo(endDate); startDate = QDateTime(QDate(2012, 7, 6), QTime(23, 55, 0)); endDate = QDateTime(QDate(2012, 7, 7), QTime(0, 5, 0)); qDebug() << "Days from startDate to endDate: " << startDate.daysTo(endDate); qSwap(startDate, endDate); // Make endDate before startDate. qDebug() << "Days from startDate to endDate: " << startDate.daysTo(endDate);
另请参阅 addDays (), secsTo ()，和 msecsTo ().
[static]
QDateTime
QDateTime::
fromCFDate
(
CFDateRef
date
)
构造新的 QDateTime containing a copy of the CFDate date .
该函数在 Qt 5.5 引入。
另请参阅 toCFDate ().
[static]
QDateTime
QDateTime::
fromMSecsSinceEpoch
(
qint64
msecs
)
Returns a datetime whose date and time are the number of milliseconds, msecs , that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ), and converted to Qt::LocalTime . On systems that do not support time zones, the time will be set as if local time were Qt::UTC .
Note that there are possible values for msecs that lie outside the valid range of QDateTime , both negative and positive. The behavior of this function is undefined for those values.
该函数在 Qt 4.7 引入。
另请参阅 toMSecsSinceEpoch () 和 setMSecsSinceEpoch ().
[static]
QDateTime
QDateTime::
fromMSecsSinceEpoch
(
qint64
msecs
,
Qt::TimeSpec
spec
,
int
offsetSeconds
= 0)
Returns a datetime whose date and time are the number of milliseconds msecs that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ) and converted to the given spec .
Note that there are possible values for msecs that lie outside the valid range of QDateTime , both negative and positive. The behavior of this function is undefined for those values.
若 spec 不是 Qt::OffsetFromUTC 那么 offsetSeconds will be ignored. If the spec is Qt::OffsetFromUTC 和 offsetSeconds is 0 then the spec will be set to Qt::UTC , i.e. an offset of 0 seconds.
若 spec is Qt::TimeZone then the spec will be set to Qt::LocalTime , i.e. the current system time zone.
该函数在 Qt 5.2 引入。
另请参阅 toMSecsSinceEpoch () 和 setMSecsSinceEpoch ().
[static]
QDateTime
QDateTime::
fromMSecsSinceEpoch
(
qint64
msecs
, const
QTimeZone
&
timeZone
)
Returns a datetime whose date and time are the number of milliseconds msecs that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ) and with the given timeZone .
该函数在 Qt 5.2 引入。
另请参阅 fromSecsSinceEpoch ().
[static]
QDateTime
QDateTime::
fromNSDate
(const
NSDate
*
date
)
构造新的 QDateTime containing a copy of the NSDate date .
该函数在 Qt 5.5 引入。
另请参阅 toNSDate ().
[static]
QDateTime
QDateTime::
fromSecsSinceEpoch
(
qint64
secs
,
Qt::TimeSpec
spec
= Qt::LocalTime,
int
offsetSeconds
= 0)
Returns a datetime whose date and time are the number of seconds secs that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ) and converted to the given spec .
Note that there are possible values for secs that lie outside the valid range of QDateTime , both negative and positive. The behavior of this function is undefined for those values.
若 spec 不是 Qt::OffsetFromUTC 那么 offsetSeconds will be ignored. If the spec is Qt::OffsetFromUTC 和 offsetSeconds is 0 then the spec will be set to Qt::UTC , i.e. an offset of 0 seconds.
若 spec is Qt::TimeZone then the spec will be set to Qt::LocalTime , i.e. the current system time zone.
该函数在 Qt 5.8 引入。
另请参阅 toSecsSinceEpoch () 和 setSecsSinceEpoch ().
[static]
QDateTime
QDateTime::
fromSecsSinceEpoch
(
qint64
secs
, const
QTimeZone
&
timeZone
)
Returns a datetime whose date and time are the number of seconds secs that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ) and with the given timeZone .
该函数在 Qt 5.8 引入。
另请参阅 fromMSecsSinceEpoch ().
[static]
QDateTime
QDateTime::
fromString
(const
QString
&
string
,
Qt::DateFormat
format
= Qt::TextDate)
返回 QDateTime represented by the string ，使用 format given, or an invalid datetime if this is not possible.
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 in Qt 5, they depend on the user's locale settings.
注意： Support for localized dates, including the format options Qt::SystemLocaleDate , Qt::SystemLocaleShortDate , Qt::SystemLocaleLongDate , Qt::LocaleDate , Qt::DefaultLocaleShortDate ，和 Qt::DefaultLocaleLongDate , shall be removed in Qt 6. Use QLocale::toDateTime () 代替。
另请参阅 toString () 和 QLocale::toDateTime ().
[static]
QDateTime
QDateTime::
fromString
(const
QString
&
string
, const
QString
&
format
,
QCalendar
cal
)
返回 QDateTime represented by the string ，使用 format given, or an invalid datetime if the string cannot be parsed.
Uses the calendar cal if supplied, else Gregorian.
In addition to the expressions, recognized in the format string to represent parts of the date and time, by QDate::fromString () 和 QTime::fromString (), this method supports:
| 表达式 | 输出 |
|---|---|
| t | the timezone (for example "CEST") |
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.
QTime time1 = QTime::fromString("131", "HHh"); // time1 is 13:00:00 QTime time1 = QTime::fromString("1apA", "1amAM"); // time1 is 01:00:00 QDateTime dateTime2 = QDateTime::fromString("M1d1y9800:01:02", "'M'M'd'd'y'yyhh:mm:ss"); // dateTime is 1 January 1998 00:01:02
If the format is not satisfied, an invalid QDateTime is returned. The expressions that don't have leading zeroes (d, M, h, m, s, z) will be greedy. This means that they will use two digits even if this will put them outside the range and/or leave too few digits for other sections.
QDateTime dateTime = QDateTime::fromString("130", "Mm"); // invalid
This could have meant 1 January 00:30.00 but the M will grab two digits.
Incorrectly specified fields of the string will cause an invalid QDateTime to be returned. For example, consider the following code, where the two digit year 12 is read as 1912 (see the table below for all field defaults); the resulting datetime is invalid because 23 April 1912 was a Tuesday, not a Monday:
QString string = "Monday, 23 April 12 22:51:41"; QString format = "dddd, d MMMM yy hh:mm:ss"; QDateTime invalid = QDateTime::fromString(string, format);
The correct code is:
QString string = "Tuesday, 23 April 12 22:51:41"; QString format = "dddd, d MMMM yy hh:mm:ss"; QDateTime valid = QDateTime::fromString(string, format);
For any field that is not represented in the format, the following defaults are used:
| Field | 默认值 |
|---|---|
| Year | 1900 |
| Month | 1 (January) |
| Day | 1 |
| Hour | 0 |
| Minute | 0 |
| Second | 0 |
例如：
QDateTime dateTime = QDateTime::fromString("1.30.1", "M.d.s"); // dateTime is January 30 in 1900 at 00:00:01. dateTime = QDateTime::fromString("12", "yy"); // dateTime is January 1 in 1912 at 00:00:00.
注意： If localized month and day names are used, please switch to using QLocale::system ().toDateTime() as QDateTime methods shall change to only recognize English (C locale) names at Qt 6.
另请参阅 toString (), QDate::fromString (), QTime::fromString ()，和 QLocale::toDateTime ().
Returns if this datetime falls in Daylight-Saving Time.
若 Qt::TimeSpec 不是 Qt::LocalTime or Qt::TimeZone then will always return false.
该函数在 Qt 5.2 引入。
另请参阅 timeSpec ().
返回
true
if both the date and the time are null; otherwise returns
false
. A null datetime is invalid.
另请参阅 QDate::isNull (), QTime::isNull ()，和 isValid ().
返回
true
if both the date and the time are valid and they are valid in the current
Qt::TimeSpec
，否则返回
false
.
若 timeSpec () 是 Qt::LocalTime or Qt::TimeZone then the date and time are checked to see if they fall in the Standard Time to Daylight-Saving Time transition hour, i.e. if the transition is at 2am and the clock goes forward to 3am then the time from 02:00:00 to 02:59:59.999 is considered to be invalid.
另请参阅 QDateTime::YearRange , QDate::isValid ()，和 QTime::isValid ().
Returns the number of milliseconds from this datetime to the other datetime. If the other datetime is earlier than this datetime, the value returned is negative.
Before performing the comparison, the two datetimes are converted to Qt::UTC to ensure that the result is correct if daylight-saving (DST) applies to one of the two datetimes and but not the other.
Returns 0 if either datetime is invalid.
另请参阅 addMSecs (), daysTo ()，和 QTime::msecsTo ().
Returns this date-time's Offset From UTC in seconds.
The result depends on timeSpec ():
Qt::UTC
The offset is 0.
Qt::OffsetFromUTC
The offset is the value originally set.
Qt::LocalTime
The local time's offset from UTC is returned.
Qt::TimeZone
The offset used by the time-zone is returned.
For the last two, the offset at this date and time will be returned, taking account of Daylight-Saving Offset unless the date precedes the start of 1970. The offset is the difference between the local time or time in the given time-zone and UTC time; it is positive in time-zones ahead of UTC (East of The Prime Meridian), negative for those behind UTC (West of The Prime Meridian).
该函数在 Qt 5.2 引入。
另请参阅 setOffsetFromUtc ().
Returns the number of seconds from this datetime to the other datetime. If the other datetime is earlier than this datetime, the value returned is negative.
Before performing the comparison, the two datetimes are converted to Qt::UTC to ensure that the result is correct if daylight-saving (DST) applies to one of the two datetimes but not the other.
Returns 0 if either datetime is invalid.
范例：
QDateTime now = QDateTime::currentDateTime(); QDateTime xmas(QDate(now.date().year(), 12, 25).startOfDay()); qDebug("There are %d seconds to Christmas", now.secsTo(xmas));
另请参阅 addSecs (), daysTo ()，和 QTime::secsTo ().
Sets the date part of this datetime to date . If no time is set yet, it is set to midnight. If date is invalid, this QDateTime becomes invalid.
另请参阅 date (), setTime ()，和 setTimeSpec ().
Sets the date and time given the number of milliseconds msecs that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ). On systems that do not support time zones this function will behave as if local time were Qt::UTC .
Note that passing the minimum of
qint64
(
std::numeric_limits<qint64>::min()
) 到
msecs
将产生未定义行为。
该函数在 Qt 4.7 引入。
另请参阅 toMSecsSinceEpoch () 和 setSecsSinceEpoch ().
设置 timeSpec () 到 Qt::OffsetFromUTC and the offset to offsetSeconds . The datetime will refer to a different point in time.
The maximum and minimum offset is 14 positive or negative hours. If offsetSeconds is larger or smaller than that, then the result is undefined.
若 offsetSeconds is 0 then the timeSpec () will be set to Qt::UTC .
该函数在 Qt 5.2 引入。
另请参阅 isValid () 和 offsetFromUtc ().
Sets the date and time given the number of seconds secs that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ). On systems that do not support time zones this function will behave as if local time were Qt::UTC .
该函数在 Qt 5.8 引入。
另请参阅 toSecsSinceEpoch () 和 setMSecsSinceEpoch ().
Sets the time part of this datetime to time 。若 time is not valid, this function sets it to midnight. Therefore, it's possible to clear any set time in a QDateTime by setting it to a default QTime :
QDateTime dt = QDateTime::currentDateTime(); dt.setTime(QTime());
另请参阅 time (), setDate ()，和 setTimeSpec ().
Sets the time specification used in this datetime to spec . The datetime will refer to a different point in time.
若 spec is Qt::OffsetFromUTC 那么 timeSpec () will be set to Qt::UTC , i.e. an effective offset of 0.
若 spec is Qt::TimeZone then the spec will be set to Qt::LocalTime , i.e. the current system time zone.
范例：
QDateTime local(QDateTime::currentDateTime()); qDebug() << "Local time is:" << local; QDateTime UTC(local); UTC.setTimeSpec(Qt::UTC); qDebug() << "UTC time is:" << UTC; qDebug() << "There are" << local.secsTo(UTC) << "seconds difference between the datetimes.";
另请参阅 timeSpec (), setDate (), setTime (), setTimeZone ()，和 Qt::TimeSpec .
Sets the time zone used in this datetime to toZone . The datetime will refer to a different point in time.
若 toZone is invalid then the datetime will be invalid.
该函数在 Qt 5.2 引入。
另请参阅 timeZone () 和 Qt::TimeSpec .
Swaps this datetime with other 。此操作非常快且从不失败。
该函数在 Qt 5.0 引入。
Returns the time part of the datetime.
另请参阅 setTime (), date ()，和 timeSpec ().
Returns the time specification of the datetime.
另请参阅 setTimeSpec (), date (), time ()，和 Qt::TimeSpec .
Returns the time zone of the datetime.
若 timeSpec () 是 Qt::LocalTime then an instance of the current system time zone will be returned. Note however that if you copy this time zone the instance will not remain in sync if the system time zone changes.
该函数在 Qt 5.2 引入。
另请参阅 setTimeZone () 和 Qt::TimeSpec .
Returns the Time Zone Abbreviation for the datetime.
若 timeSpec () 是 Qt::UTC this will be "UTC".
若 timeSpec () 是 Qt::OffsetFromUTC this will be in the format "UTC[+-]00:00".
若 timeSpec () 是 Qt::LocalTime then the host system is queried for the correct abbreviation.
Note that abbreviations may or may not be localized.
Note too that the abbreviation is not guaranteed to be a unique value, i.e. different time zones may have the same abbreviation.
该函数在 Qt 5.2 引入。
另请参阅 timeSpec ().
Creates a CFDate from a QDateTime . The caller owns the CFDate object and is responsible for releasing it.
该函数在 Qt 5.5 引入。
另请参阅 fromCFDate ().
Returns a datetime containing the date and time information in this datetime, but specified using the Qt::LocalTime definition.
范例：
QDateTime UTC(QDateTime::currentDateTimeUtc()); QDateTime local(UTC.toLocalTime()); qDebug() << "UTC time is:" << UTC; qDebug() << "Local time is:" << local; qDebug() << "No difference between times:" << UTC.secsTo(local);
另请参阅 toTimeSpec ().
Returns the datetime as the number of milliseconds that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ).
On systems that do not support time zones, this function will behave as if local time were Qt::UTC .
The behavior for this function is undefined if the datetime stored in this object is not valid. However, for all valid dates, this function returns a unique value.
该函数在 Qt 4.7 引入。
另请参阅 toSecsSinceEpoch () 和 setMSecsSinceEpoch ().
Creates an NSDate from a QDateTime . The NSDate object is autoreleased.
该函数在 Qt 5.5 引入。
另请参阅 fromNSDate ().
Returns a copy of this datetime converted to a spec of Qt::OffsetFromUTC 采用给定 offsetSeconds .
若 offsetSeconds equals 0 then a UTC datetime will be returned
该函数在 Qt 5.2 引入。
另请参阅 setOffsetFromUtc (), offsetFromUtc ()，和 toTimeSpec ().
Returns the datetime as the number of seconds that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time ( Qt::UTC ).
On systems that do not support time zones, this function will behave as if local time were Qt::UTC .
The behavior for this function is undefined if the datetime stored in this object is not valid. However, for all valid dates, this function returns a unique value.
该函数在 Qt 5.8 引入。
另请参阅 toMSecsSinceEpoch () 和 setSecsSinceEpoch ().
这是重载函数。
Returns the datetime as a string in the format 给定。
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 "Wed May 20 03:40:13 1998".
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-ddTHH:mm:ss[Z|[+|-]HH:mm], depending on the timeSpec () of the QDateTime 。若 timeSpec () 是 Qt::UTC , Z will be appended to the string; if the timeSpec () 是 Qt::OffsetFromUTC , the offset in hours and minutes from UTC will be appended to the string. To include milliseconds in the ISO 8601 date, use the format Qt::ISODateWithMs , which corresponds to yyyy-MM-ddTHH:mm:ss.zzz[Z|[+|-]HH:mm].
format options Qt::SystemLocaleDate , Qt::SystemLocaleShortDate and Qt::SystemLocaleLongDate shall be removed in Qt 6. Their use should be replaced with QLocale::system().toString(datetime, QLocale::ShortFormat) or QLocale::system().toString(datetime, QLocale::LongFormat) .
format options Qt::LocaleDate , Qt::DefaultLocaleShortDate and Qt::DefaultLocaleLongDate shall be removed in Qt 6. Their use should be replaced with QLocale().toString(datetime, QLocale::ShortFormat) or QLocale().toString(datetime, QLocale::LongFormat) .
若 format is Qt::RFC2822Date , the string is formatted following RFC 2822 .
If the datetime is invalid, an empty string will be returned.
警告： Qt::ISODate format is only valid for years in the range 0 to 9999.
另请参阅 fromString (), QDate::toString (), QTime::toString ()，和 QLocale::toString ().
Returns a copy of this datetime converted to the given time spec .
若 spec is Qt::OffsetFromUTC then it is set to Qt::UTC . To set to a spec of Qt::OffsetFromUTC use toOffsetFromUtc ().
若 spec is Qt::TimeZone then it is set to Qt::LocalTime , i.e. the local Time Zone.
范例：
QDateTime local(QDateTime::currentDateTime()); QDateTime UTC(local.toTimeSpec(Qt::UTC)); qDebug() << "Local time is:" << local; qDebug() << "UTC time is:" << UTC; qDebug() << "No difference between times:" << local.secsTo(UTC);
另请参阅 timeSpec (), toTimeZone ()，和 toOffsetFromUtc ().
Returns a copy of this datetime converted to the given timeZone
该函数在 Qt 5.2 引入。
另请参阅 timeZone () 和 toTimeSpec ().
Returns a datetime containing the date and time information in this datetime, but specified using the Qt::UTC definition.
范例：
QDateTime local(QDateTime::currentDateTime()); QDateTime UTC(local.toUTC()); qDebug() << "Local time is:" << local; qDebug() << "UTC time is:" << UTC; qDebug() << "No difference between times:" << local.secsTo(UTC);
另请参阅 toTimeSpec ().
返回
true
if this datetime is different from the
other
datetime; otherwise returns
false
.
Two datetimes are different if either the date, the time, or the time zone components are different. Since 5.14, any invalid datetime is less than all valid datetimes.
另请参阅 operator== ().
返回
true
if this datetime is earlier than the
other
datetime; otherwise returns
false
.
返回
true
if this datetime is earlier than or equal to the
other
datetime; otherwise returns
false
.
返回
true
if this datetime is equal to the
other
datetime; otherwise returns
false
.
Since 5.14, all invalid datetimes are equal to one another and differ from all other datetimes.
另请参阅 operator!= ().
返回
true
if this datetime is later than the
other
datetime; otherwise returns
false
.
返回
true
if this datetime is later than or equal to the
other
datetime; otherwise returns
false
.
写入 dateTime 到 out stream.
另请参阅 序列化 Qt 数据类型 .
Reads a datetime from the stream in into dateTime .
另请参阅 序列化 Qt 数据类型 .