QDateTime 类提供日期和时间功能。 更多...
| 头： | #include <QDateTime> |
| CMake: |
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core) |
| qmake: | QT += core |
注意： 此类的所有函数 可重入 .
| enum class | YearRange { First, Last } |
| QDateTime () | |
| QDateTime (QDate date , QTime time , const QTimeZone & timeZone ) | |
| QDateTime (QDate date , QTime time ) | |
| QDateTime (const QDateTime & other ) | |
| QDateTime (QDateTime && other ) | |
| ~QDateTime () | |
| QDateTime | addDays (qint64 ndays ) const |
| QDateTime | addDuration (std::chrono::milliseconds msecs ) 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 (QDate date ) |
| void | setMSecsSinceEpoch (qint64 msecs ) |
| void | setSecsSinceEpoch (qint64 secs ) |
| void | setTime (QTime time ) |
| void | setTimeZone (const QTimeZone & toZone ) |
| void | swap (QDateTime & other ) |
| QTime | time () const |
| QTimeZone | timeRepresentation () 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 |
| std::chrono::sys_time<std::chrono::milliseconds> | toStdSysMilliseconds () const |
| std::chrono::sys_seconds | toStdSysSeconds () const |
| QString | toString (const QString & format , QCalendar cal = QCalendar()) const |
| QString | toString (Qt::DateFormat format = Qt::TextDate) const |
| QString | toString (QStringView format , QCalendar cal = QCalendar()) const |
| QDateTime | toTimeZone (const QTimeZone & timeZone ) const |
| QDateTime | toUTC () const |
| QDateTime & | operator+= (std::chrono::milliseconds duration ) |
| QDateTime & | operator-= (std::chrono::milliseconds duration ) |
| QDateTime & | operator= (const QDateTime & other ) |
| QDateTime | currentDateTime (const QTimeZone & zone ) |
| QDateTime | currentDateTime () |
| QDateTime | currentDateTimeUtc () |
| qint64 | currentMSecsSinceEpoch () |
| qint64 | currentSecsSinceEpoch () |
| QDateTime | fromCFDate (CFDateRef date ) |
| QDateTime | fromMSecsSinceEpoch (qint64 msecs , const QTimeZone & timeZone ) |
| QDateTime | fromMSecsSinceEpoch (qint64 msecs ) |
| QDateTime | fromNSDate (const NSDate * date ) |
| QDateTime | fromSecsSinceEpoch (qint64 secs , const QTimeZone & timeZone ) |
| QDateTime | fromSecsSinceEpoch (qint64 secs ) |
| QDateTime | fromStdLocalTime (const std::chrono::local_time<std::chrono::milliseconds> & time ) |
| QDateTime | fromStdTimePoint (const std::chrono::time_point<Clock, Duration> & time ) |
| QDateTime | fromStdTimePoint (const std::chrono::local_time<std::chrono::milliseconds> & time ) |
| QDateTime | fromStdZonedTime (const int & time ) |
| QDateTime | fromString (const QString & string , Qt::DateFormat format = Qt::TextDate) |
| QDateTime | fromString (QStringView string , Qt::DateFormat format = Qt::TextDate) |
| QDateTime | fromString (QStringView string , QStringView format , QCalendar cal = QCalendar()) |
| QDateTime | fromString (const QString & string , QStringView format , QCalendar cal = QCalendar()) |
| QDateTime | fromString (const QString & string , const QString & format , QCalendar cal = QCalendar()) |
| bool | operator!= (const QDateTime & lhs , const QDateTime & rhs ) |
| QDateTime | operator+ (const QDateTime & dateTime , std::chrono::milliseconds duration ) |
| QDateTime | operator+ (std::chrono::milliseconds duration , const QDateTime & dateTime ) |
| std::chrono::milliseconds | operator- (const QDateTime & lhs , const QDateTime & rhs ) |
| QDateTime | operator- (const QDateTime & dateTime , std::chrono::milliseconds duration ) |
| bool | operator< (const QDateTime & lhs , const QDateTime & rhs ) |
| QDataStream & | operator<< (QDataStream & out , const QDateTime & dateTime ) |
| bool | operator<= (const QDateTime & lhs , const QDateTime & rhs ) |
| bool | operator== (const QDateTime & lhs , const QDateTime & rhs ) |
| bool | operator> (const QDateTime & lhs , const QDateTime & rhs ) |
| bool | operator>= (const QDateTime & lhs , const QDateTime & rhs ) |
| QDataStream & | operator>> (QDataStream & in , QDateTime & dateTime ) |
A QDateTime object encodes a calendar date and a clock time (a "datetime") in accordance with a time representation. 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 . Each of these time representations can be encapsulated in a suitable instance of the QTimeZone class. For example, a time zone of "Europe/Berlin" will apply the daylight-saving rules as used in Germany. In contrast, a fixed 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 complications. When using either local time or a specified time zone, time-zone transitions (see below ) are taken into account. A QDateTime's timeSpec () will tell you which of the four types of time representation is in use; its timeRepresentation () provides a full representation of that time representation, as a QTimeZone .
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 () or 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 the start, in UTC of the year 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 date and time with respect to a specific time representation, such as local time (its default).
QDateTime::currentDateTimeUtc
() returns a QDateTime that expresses the current date and time with respect to UTC; it is equivalent to
QDateTime::currentDateTime(QTimeZone::UTC)
.
The 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
toTimeZone
() to re-express a datetime in terms of a different time representation. By passing a lightweight
QTimeZone
that represents local time, UTC or a fixed offset from UTC, you can convert the datetime to use the corresponding time representation; or you can pass a full time zone (whose
timeSpec
() 是
Qt::TimeZone
) to use that instead.
注意： QDateTime does not account for leap seconds.
注意： All conversion to and from string formats is done using the C locale. For localized conversions, see QLocale .
注意： There is no year 0 in the Gregorian calendar. 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 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 time representation used.
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. However, building Qt with the ICU library will equipe QTimeZone with the same timezone database as is used on Unix.
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 second to 01:59:59 will get 03:00:00.
For datetimes that the system
time_t
can represent (from 1901-12-14 to 2038-01-18 on systems with 32-bit
time_t
; for the full range QDateTime can represent if the type is 64-bit), the standard system APIs are used to determine local time's offset from UTC. For datetimes not handled by these system APIs,
QTimeZone::systemTimeZone
() is used. In either case, the offset information used depends on the system and may be incomplete or, for past times, historically inaccurate. In any case, for future dates, the local time zone's offsets and DST rules may change before that date comes around.
Offsets from UTC are measured in seconds east of Greenwich. The moment described by a particular date and time, such as noon on a particular day, depends on the time representation used. Those with a higher offset from UTC describe an earlier moment, and those with a lower offset a later moment, by any given combination of date and time.
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 has an offset outside the range of ±14 hours and all known offsets are multiples of five minutes.
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.
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 |
若日期时间无效，返回空字符串。
注意： Day and month names as well as AM/PM indicators are given in English (C locale). To get localized month and day names and localized forms of AM/PM, use QLocale::system ().toDateTime().
另请参阅 fromString (), QDate::toString (), QTime::toString ()，和 QLocale::toString ().
Constructs a null datetime, nominally using local time.
A null datetime is invalid, since its date and time are invalid.
另请参阅 isValid (), setMSecsSinceEpoch (), setDate (), setTime ()，和 setTimeZone ().
构造日期时间采用给定 date and time , using the time representation described by timeZone .
若 date 有效和 time is not, the time will be set to midnight. If timeZone is invalid then the datetime will be invalid.
[since 6.5]
QDateTime::
QDateTime
(
QDate
date
,
QTime
time
)
构造日期时间采用给定 date and time , using local time.
若 date 有效和 time is not, midnight will be used as the time.
该函数在 Qt 6.5 引入。
构造副本为 other datetime.
Moves the content of the temporary other datetime to this object and leaves other in an unspecified (but proper) state.
销毁日期时间。
返回 QDateTime 对象包含日期时间 ndays days later than the datetime of this object (or earlier if ndays is negative).
若 timeSpec () 是 Qt::LocalTime or Qt::TimeZone 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 ().
[since 6.4]
QDateTime
QDateTime::
addDuration
(
std::chrono::milliseconds
msecs
) const
返回 QDateTime 对象包含日期时间 msecs milliseconds later than the datetime of this object (or earlier if msecs is negative).
If this datetime is invalid, an invalid datetime will be returned.
注意：
Adding durations expressed in
std::chrono::months
or
std::chrono::years
does not yield the same result obtained by using
addMonths
() 或
addYears
(). The former are fixed durations, calculated in relation to the solar year; the latter use the Gregorian calendar definitions of months/years.
该函数在 Qt 6.4 引入。
另请参阅 addMSecs (), msecsTo (), addDays (), addMonths ()，和 addYears ().
返回 QDateTime 对象包含日期时间 msecs milliseconds 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 对象包含日期时间 nmonths months later than the datetime of this object (or earlier if nmonths is negative).
若 timeSpec () 是 Qt::LocalTime or Qt::TimeZone 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 对象包含日期时间 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 对象包含日期时间 nyears years later than the datetime of this object (or earlier if nyears is negative).
若 timeSpec () 是 Qt::LocalTime or Qt::TimeZone 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, since 6.5]
QDateTime
QDateTime::
currentDateTime
(const
QTimeZone
&
zone
)
Returns the system clock's current datetime, using the time representation described by zone 。若 zone is omitted, local time is used.
该函数在 Qt 6.5 引入。
另请参阅 currentDateTimeUtc (), QDate::currentDate (), QTime::currentTime ()，和 toTimeSpec ().
[static]
QDateTime
QDateTime::
currentDateTime
()
这是重载函数。
[static]
QDateTime
QDateTime::
currentDateTimeUtc
()
Returns the system clock's current datetime, expressed in terms of UTC.
相当于
currentDateTime(QTimeZone::UTC)
.
另请参阅 currentDateTime (), QDate::currentDate (), QTime::currentTime ()，和 toTimeSpec ().
[static]
qint64
QDateTime::
currentMSecsSinceEpoch
()
Returns the current number of milliseconds since the start, in UTC, of the year 1970.
This number is like the POSIX time_t variable, but expressed in milliseconds instead of seconds.
另请参阅 currentDateTime (), currentDateTimeUtc ()，和 toTimeSpec ().
[static]
qint64
QDateTime::
currentSecsSinceEpoch
()
Returns the number of seconds since the start, in UTC, of the year 1970.
This number is like the POSIX time_t variable.
另请参阅 currentMSecsSinceEpoch ().
返回 datetime 的日期部分。
另请参阅 setDate (), time ()，和 timeRepresentation ().
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 .
另请参阅 toCFDate ().
[static]
QDateTime
QDateTime::
fromMSecsSinceEpoch
(
qint64
msecs
, const
QTimeZone
&
timeZone
)
这是重载函数。
Returns a datetime representing a moment the given number msecs of milliseconds after the start, in UTC, of the year 1970, described as specified by timeZone . The default time representation is local time.
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.
另请参阅 fromSecsSinceEpoch (), toMSecsSinceEpoch ()，和 setMSecsSinceEpoch ().
[static, since 6.5]
QDateTime
QDateTime::
fromMSecsSinceEpoch
(
qint64
msecs
)
这是重载函数。
该函数在 Qt 6.5 引入。
[static]
QDateTime
QDateTime::
fromNSDate
(const
NSDate
*
date
)
构造新的 QDateTime containing a copy of the NSDate date .
另请参阅 toNSDate ().
[static]
QDateTime
QDateTime::
fromSecsSinceEpoch
(
qint64
secs
, const
QTimeZone
&
timeZone
)
这是重载函数。
Returns a datetime representing a moment the given number secs of seconds after the start, in UTC, of the year 1970, described as specified by timeZone . The default time representation is local time.
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.
另请参阅 fromMSecsSinceEpoch (), toSecsSinceEpoch ()，和 setSecsSinceEpoch ().
[static, since 6.5]
QDateTime
QDateTime::
fromSecsSinceEpoch
(
qint64
secs
)
这是重载函数。
该函数在 Qt 6.5 引入。
[static, since 6.4]
QDateTime
QDateTime::
fromStdLocalTime
(const
std::chrono::local_time
<
std::chrono::milliseconds
> &
time
)
Constructs a datetime whose date and time are the number of milliseconds represented by time , counted since 1970-01-01T00:00:00.000 in local time ( Qt::LocalTime ).
注意： This function requires C++20.
该函数在 Qt 6.4 引入。
另请参阅 toStdSysMilliseconds () 和 fromMSecsSinceEpoch ().
[static, since 6.4]
template <typename Clock, typename Duration>
QDateTime
QDateTime::
fromStdTimePoint
(const
std::chrono::time_point
<
Clock
,
Duration
> &
time
)
Constructs a datetime representing the same point in time as time ，使用 Qt::UTC as its specification.
The clock of
time
must be compatible with
std::chrono::system_clock
, and the duration type must be convertible to
std::chrono::milliseconds
.
注意： This function requires C++20.
该函数在 Qt 6.4 引入。
另请参阅 toStdSysMilliseconds () 和 fromMSecsSinceEpoch ().
[static, since 6.4]
QDateTime
QDateTime::
fromStdTimePoint
(const
std::chrono::local_time
<
std::chrono::milliseconds
> &
time
)
Constructs a datetime whose date and time are the number of milliseconds represented by time , counted since 1970-01-01T00:00:00.000 in local time ( Qt::LocalTime ).
注意： This function requires C++20.
该函数在 Qt 6.4 引入。
另请参阅 toStdSysMilliseconds () 和 fromMSecsSinceEpoch ().
[static, since 6.4]
QDateTime
QDateTime::
fromStdZonedTime
(const
int
&
time
)
Constructs a datetime representing the same point in time as time . The result will be expressed in time 's time zone.
注意： This function requires C++20.
该函数在 Qt 6.4 引入。
另请参阅 QTimeZone , toStdSysMilliseconds ()，和 fromMSecsSinceEpoch ().
[static]
QDateTime
QDateTime::
fromString
(const
QString
&
string
,
Qt::DateFormat
format
= Qt::TextDate)
返回 QDateTime 表示通过 string ，使用 format given, or an invalid datetime if this is not possible.
Note for Qt::TextDate : only English short month names (e.g. "Jan" in short form or "January" in long form) are recognized.
另请参阅 toString () 和 QLocale::toDateTime ().
[static, since 6.0]
QDateTime
QDateTime::
fromString
(
QStringView
string
,
Qt::DateFormat
format
= Qt::TextDate)
这是重载函数。
该函数在 Qt 6.0 引入。
[static, since 6.0]
QDateTime
QDateTime::
fromString
(
QStringView
string
,
QStringView
format
,
QCalendar
cal
= QCalendar())
这是重载函数。
该函数在 Qt 6.0 引入。
[static, since 6.0]
QDateTime
QDateTime::
fromString
(const
QString
&
string
,
QStringView
format
,
QCalendar
cal
= QCalendar())
这是重载函数。
该函数在 Qt 6.0 引入。
[static]
QDateTime
QDateTime::
fromString
(const
QString
&
string
, const
QString
&
format
,
QCalendar
cal
= QCalendar())
返回 QDateTime 表示通过 string ，使用 format given, or an invalid datetime if the string cannot be parsed.
使用日历 cal 若有供给，否则高利历 (公历)。
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 (offset, name, "Z" or offset with "UTC" prefix) |
| tt | the timezone in offset format with no colon between hours and minutes (for example "+0200") |
| ttt | the timezone in offset format with a colon between hours and minutes (for example "+02:00") |
| tttt | the timezone name (for example "Europe/Berlin"). The name recognized are those known to QTimeZone , which may depend on the operating system in use. |
If no 't' format specifier is present, the system's local time-zone is used. For the defaults of all other fields, see QDate::fromString () 和 QTime::fromString ().
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.
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. If the format is satisfied but string represents an invalid datetime (e.g. in a gap skipped by a time-zone transition), an invalid QDateTime is returned, whose toMSecsSinceEpoch () represents a near-by datetime that is valid. Passing that to fromMSecsSinceEpoch() will produce a valid datetime that isn't faithfully represented by the string parsed.
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 (or three, for z) 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);
注意： Day and month names as well as AM/PM indicators must be given in English (C locale). If localized month and day names or localized forms of AM/PM are to be recognized, use QLocale::system ().toDateTime().
注意：
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
'tttttt'
would match
"Europe/BerlinEurope/Berlin"
and set the zone to Berlin time; if the datetime string contained "Europe/BerlinZ" it would "match" but produce an inconsistent result, leading to an invalid datetime.
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.
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 this datetime represents a definite moment, otherwise
false
.
A datetime is valid if both its date and its time are valid and the time representation used gives a valid meaning to their combination. When the time representation is a specific time-zone or local time, there may be times on some dates that the zone skips in its representation, as when a daylight-saving transition skips an hour (typically during a night in spring). For example, if DST ends at 2am with the clock advancing to 3am, then datetimes from 02:00:00 to 02:59:59.999 on that day are 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.
返回 0 若日期时间无效。
另请参阅 addMSecs (), daysTo ()，和 QTime::msecsTo ().
Returns this datetime's Offset From UTC in seconds.
结果从属 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. 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).
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.
返回 0 若日期时间无效。
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 setTimeZone ().
Sets the datetime to represent a moment a given number, msecs , of milliseconds after the start, in UTC, of the year 1970.
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。
另请参阅 setSecsSinceEpoch (), toMSecsSinceEpoch ()，和 fromMSecsSinceEpoch ().
Sets the datetime to represent a moment a given number, secs , of seconds after the start, in UTC, of the year 1970.
On systems that do not support time zones, this function will behave as if local time were Qt::UTC .
另请参阅 setMSecsSinceEpoch (), toSecsSinceEpoch ()，和 fromSecsSinceEpoch ().
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 setTimeZone ().
Sets the time zone used in this datetime to toZone .
The datetime may refer to a different point in time. It uses the time representation of toZone , which may change the meaning of its unchanged date () 和 time ().
若
toZone
is invalid then the datetime will be invalid. Otherwise, this datetime's
timeSpec
() after the call will match
toZone.timeSpec()
.
另请参阅 timeRepresentation (), timeZone ()，和 Qt::TimeSpec .
Swaps this datetime with other 。此操作非常快且从不失败。
Returns the time part of the datetime.
另请参阅 setTime (), date ()，和 timeRepresentation ().
[since 6.5]
QTimeZone
QDateTime::
timeRepresentation
() const
返回 QTimeZone identifying how this datetime represents time.
The timeSpec () of the returned QTimeZone will coincide with that of this datetime; if it is not Qt::TimeZone then the returned QTimeZone is a time representation. When their timeSpec () 是 Qt::OffsetFromUTC , the returned QTimeZone 's fixedSecondsAheadOfUtc() supplies the offset. When timeSpec () 是 Qt::TimeZone ， QTimeZone object itself is the full representation of that time zone.
该函数在 Qt 6.5 引入。
另请参阅 timeZone (), setTimeZone ()，和 QTimeZone::asBackendZone ().
Returns the time specification of the datetime.
This classifies its time representation as local time, UTC, a fixed offset from UTC (without indicating the offset) or a time zone (without giving the details of that time zone). Equivalent to
timeRepresentation().timeSpec()
.
另请参阅 setTimeSpec (), timeRepresentation (), date ()，和 time ().
Returns the time zone of the datetime.
The result is the same as
timeRepresentation().asBackendZone()
. In all cases, the result's
timeSpec
() 是
Qt::TimeZone
.
当 timeSpec () 是 Qt::LocalTime , the result will describe local time at the time this method was called. It will not reflect subsequent changes to the system time zone, even when the QDateTime from which it was obtained does.
另请参阅 timeRepresentation (), setTimeZone (), Qt::TimeSpec ，和 QTimeZone::asBackendZone ().
Returns the Time Zone Abbreviation for this datetime.
The returned string depends on timeSpec ():
注意： The abbreviation is not guaranteed to be unique, i.e. different time zones may have the same abbreviation. For Qt::LocalTime and Qt::TimeZone , when returned by the host system, the abbreviation may be localized.
另请参阅 timeSpec () 和 QTimeZone::abbreviation ().
创建 CFDate 从 QDateTime .
The caller owns the CFDate object and is responsible for releasing it.
另请参阅 fromCFDate ().
Returns a copy of this datetime converted to local time.
The result represents the same moment in time as, and is equal to, this datetime.
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 toTimeZone (), toUTC ()，和 toOffsetFromUtc ().
Returns the datetime as a number of milliseconds after the start, in UTC, of the year 1970.
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.
另请参阅 toSecsSinceEpoch (), setMSecsSinceEpoch ()，和 fromMSecsSinceEpoch ().
创建 NSDate 从 QDateTime .
The NSDate object is autoreleased.
另请参阅 fromNSDate ().
Returns a copy of this datetime converted to a spec of
Qt::OffsetFromUTC
采用给定
offsetSeconds
. Equivalent to
toTimeZone(QTimeZone::fromSecondsAheadOfUtc(offsetSeconds))
.
若 offsetSeconds equals 0 then a UTC datetime will be returned.
The result represents the same moment in time as, and is equal to, this datetime.
另请参阅 setOffsetFromUtc (), offsetFromUtc ()，和 toTimeZone ().
Returns the datetime as a number of seconds after the start, in UTC, of the year 1970.
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.
另请参阅 toMSecsSinceEpoch (), fromSecsSinceEpoch ()，和 setSecsSinceEpoch ().
[since 6.4]
std::chrono::sys_time
<
std::chrono::milliseconds
> QDateTime::
toStdSysMilliseconds
() const
Converts this datetime object to the equivalent time point expressed in milliseconds, using
std::chrono::system_clock
as a clock.
注意： This function requires C++20.
该函数在 Qt 6.4 引入。
另请参阅 fromStdTimePoint () 和 toMSecsSinceEpoch ().
[since 6.4]
std::chrono::sys_seconds
QDateTime::
toStdSysSeconds
() const
Converts this datetime object to the equivalent time point expressed in seconds, using
std::chrono::system_clock
as a clock.
注意： This function requires C++20.
该函数在 Qt 6.4 引入。
另请参阅 fromStdTimePoint () 和 toSecsSinceEpoch ().
这是重载函数。
以字符串形式返回日期时间按 format 给定。
若 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 "Wed May 20 03:40:13 1998". For localized formatting, see QLocale::toString ().
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 () 对于 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].
若 format is Qt::RFC2822Date , the string is formatted following RFC 2822 .
若日期时间无效，返回空字符串。
警告： The 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 timeZone .
The result represents the same moment in time as, and is equal to, this datetime.
The result describes the moment in time in terms of timeZone 's time representation. For example:
QDateTime local(QDateTime::currentDateTime()); QDateTime UTC(local.toTimeSpec(QTimeZone::UTC)); qDebug() << "Local time is:" << local; qDebug() << "UTC time is:" << UTC; qDebug() << "No difference between times represented:" << local.secsTo(UTC);
若
timeZone
is invalid then the datetime will be invalid. Otherwise the returned datetime's
timeSpec
() will match
timeZone.timeSpec()
.
另请参阅 timeRepresentation (), toLocalTime (), toUTC ()，和 toOffsetFromUtc ().
Returns a copy of this datetime converted to UTC.
The result represents the same moment in time as, and is equal to, this datetime.
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 toTimeZone (), toLocalTime ()，和 toOffsetFromUtc ().
[since 6.4]
QDateTime
&QDateTime::
operator+=
(
std::chrono::milliseconds
duration
)
Modifies this datetime object by adding the given duration . The updated object will be later if duration is positive, or earlier if it is negative.
If this datetime is invalid, this function has no effect.
Returns a reference to this datetime object.
该函数在 Qt 6.4 引入。
另请参阅 addMSecs ().
[since 6.4]
QDateTime
&QDateTime::
operator-=
(
std::chrono::milliseconds
duration
)
Modifies this datetime object by subtracting the given duration . The updated object will be earlier if duration is positive, or later if it is negative.
If this datetime is invalid, this function has no effect.
Returns a reference to this datetime object.
该函数在 Qt 6.4 引入。
另请参阅 addMSecs .
拷贝 other datetime into this and returns this copy.
[since 6.4]
QDateTime
operator+
(const
QDateTime
&
dateTime
,
std::chrono::milliseconds
duration
)
[since 6.4]
QDateTime
operator+
(
std::chrono::milliseconds
duration
, const
QDateTime
&
dateTime
)
返回 QDateTime 对象包含日期时间 duration milliseconds later than dateTime (or earlier if duration is negative).
若 dateTime is invalid, an invalid datetime will be returned.
该函数在 Qt 6.4 引入。
另请参阅 addMSecs ().
返回
true
if
lhs
is different from
rhs
；否则返回
false
.
Two datetimes are different if either the date, the time, or the time zone components are different. Since 5.14, all invalid datetime are equal (and less than all valid datetimes).
另请参阅 operator== ().
[since 6.4]
std::chrono::milliseconds
operator-
(const
QDateTime
&
lhs
, const
QDateTime
&
rhs
)
Returns the number of milliseconds between lhs and rhs 。若 lhs is earlier than rhs , the result will be negative.
返回 0 若日期时间无效。
该函数在 Qt 6.4 引入。
另请参阅 msecsTo ().
[since 6.4]
QDateTime
operator-
(const
QDateTime
&
dateTime
,
std::chrono::milliseconds
duration
)
返回 QDateTime 对象包含日期时间 duration milliseconds earlier than dateTime (or later if duration is negative).
若 dateTime is invalid, an invalid datetime will be returned.
该函数在 Qt 6.4 引入。
另请参阅 addMSecs ().
返回
true
if
lhs
is earlier than
rhs
；否则返回
false
.
另请参阅 operator== ().
写入 dateTime 到 out stream.
另请参阅 序列化 Qt 数据类型 .
返回
true
if
lhs
is earlier than or equal to
rhs
；否则返回
false
.
另请参阅 operator== ().
返回
true
if
lhs
如同
rhs
；否则返回
false
.
Two datetimes are different if either the date, the time, or the time zone components are different. Since 5.14, all invalid datetime are equal (and less than all valid datetimes).
另请参阅 operator!= (), operator< (), operator<= (), operator> ()，和 operator>= ().
返回
true
if
lhs
is later than
rhs
；否则返回
false
.
另请参阅 operator== ().
返回
true
if
lhs
is later than or equal to
rhs
；否则返回
false
.
另请参阅 operator== ().
Reads a datetime from the stream in into dateTime .
另请参阅 序列化 Qt 数据类型 .