QDateTime Class

The QDateTime class provides date and time functions. More...

Header: #include <QDateTime>
CMake: find_package(Qt6 COMPONENTS Core REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake: QT += core

Note: All functions in this class are reentrant.

Public Types

enum class YearRange { First, Last }

Public Functions

QDateTime(QDateTime &&other)
QDateTime(const QDateTime &other)
QDateTime(QDate date, QTime time, const QTimeZone &timeZone)
QDateTime(QDate date, QTime time, Qt::TimeSpec spec = Qt::LocalTime, int offsetSeconds = 0)
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(QDate date)
void setMSecsSinceEpoch(qint64 msecs)
void setOffsetFromUtc(int offsetSeconds)
void setSecsSinceEpoch(qint64 secs)
void setTime(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, QCalendar cal = QCalendar()) const
QString toString(Qt::DateFormat format = Qt::TextDate) const
QString toString(QStringView format, QCalendar cal = QCalendar()) const
QDateTime toTimeSpec(Qt::TimeSpec spec) const
QDateTime toTimeZone(const QTimeZone &timeZone) const
QDateTime toUTC() const

Static Public Members

QDateTime currentDateTime()
QDateTime currentDateTimeUtc()
qint64 currentMSecsSinceEpoch()
qint64 currentSecsSinceEpoch()
QDateTime fromCFDate(CFDateRef date)
QDateTime fromMSecsSinceEpoch(qint64 msecs, Qt::TimeSpec spec = Qt::LocalTime, 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(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)
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)

Detailed Description

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, to 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. 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() or fromMSecsSinceEpoch(). The date and time can be changed with setDate() and 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.

The date() and time() functions provide access to the date and time parts of the datetime. The same information is provided in textual format by the toString() function.

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() and addYears(). The 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.

Use 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.

Note: QDateTime does not account for leap seconds.

Remarks

Note: All conversion to and from string formats is done using the C locale. For localized conversions, see QLocale.

Note: 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.

Range of Valid Dates

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.

Use of Timezones

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 documentation for more details.

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.

Daylight-Saving Time (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.

For date-times 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 date-times 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

There is no explicit size restriction on an offset from UTC, but there is an implicit limit imposed when using the toString() and 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.

See also QDate, QTime, QDateTimeEdit, and QTimeZone.

Member Type Documentation

[since 5.14] enum class QDateTime::YearRange

This enumerated type describes the range of years (in the Gregorian calendar) representable by QDateTime:

ConstantValueDescription
QDateTime::YearRange::First-292275056The later parts of this year are representable
QDateTime::YearRange::Last+292278994The 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.

Note: 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.

This enum was introduced or modified in Qt 5.14.

See also isValid() and QDate.

Member Function Documentation

QString QDateTime::toString(QStringView format, QCalendar cal = QCalendar()) const

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

Returns the datetime as a string. The format parameter determines the format of the result string. If cal is supplied, it determines the calendar used to represent the date; it defaults to Gregorian. See QTime::toString() and 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):

FormatResult
dd.MM.yyyy21.05.2001
ddd MMMM d yyTue May 21 01
hh:mm:ss.zzz14:13:09.120
hh:mm:ss.z14:13:09.12
h:m:s ap2:13:9 pm

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

Note: 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().

See also fromString(), QDate::toString(), QTime::toString(), and QLocale::toString().

[since 5.8] QDateTime::QDateTime(QDateTime &&other)

Moves the content of the temporary other datetime to this object and leaves other in an unspecified (but proper) state.

This function was introduced in Qt 5.8.

QDateTime::QDateTime(const QDateTime &other)

Constructs a copy of the other datetime.

[since 5.2] QDateTime::QDateTime(QDate date, QTime time, const QTimeZone &timeZone)

Constructs a datetime with the given date and time, using the Time Zone specified by timeZone.

If date is valid and time is not, the time will be set to 00:00:00.

If timeZone is invalid then the datetime will be invalid.

This function was introduced in Qt 5.2.

QDateTime::QDateTime(QDate date, QTime time, Qt::TimeSpec spec = Qt::LocalTime, int offsetSeconds = 0)

Constructs a datetime with the given date and time, using the time specification defined by spec and offsetSeconds seconds.

If date is valid and time is not, the time will be set to midnight.

If the spec is not Qt::OffsetFromUTC then offsetSeconds will be ignored.

If the spec is Qt::OffsetFromUTC and offsetSeconds is 0 then the timeSpec() will be set to Qt::UTC, i.e. an offset of 0 seconds.

If 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.

QDateTime::QDateTime()

Constructs a null datetime.

A null datetime is invalid, since its date and time are invalid.

See also isValid().

QDateTime &QDateTime::operator=(const QDateTime &other)

Makes a copy of the other datetime and returns a reference to the copy.

QDateTime::~QDateTime()

Destroys the datetime.

QDateTime QDateTime::addDays(qint64 ndays) const

Returns a QDateTime object containing a datetime ndays days later than the datetime of this object (or earlier if ndays is negative).

If the timeSpec() is 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.

See also daysTo(), addMonths(), addYears(), and addSecs().

QDateTime QDateTime::addMSecs(qint64 msecs) const

Returns a QDateTime object containing a datetime 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.

See also addSecs(), msecsTo(), addDays(), addMonths(), and addYears().

QDateTime QDateTime::addMonths(int nmonths) const

Returns a QDateTime object containing a datetime nmonths months later than the datetime of this object (or earlier if nmonths is negative).

If the timeSpec() is 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.

See also daysTo(), addDays(), addYears(), and addSecs().

QDateTime QDateTime::addSecs(qint64 s) const

Returns a 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.

See also addMSecs(), secsTo(), addDays(), addMonths(), and addYears().

QDateTime QDateTime::addYears(int nyears) const

Returns a QDateTime object containing a datetime nyears years later than the datetime of this object (or earlier if nyears is negative).

If the timeSpec() is 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.

See also daysTo(), addDays(), addMonths(), and addSecs().

[static] QDateTime QDateTime::currentDateTime()

Returns the current datetime, as reported by the system clock, in the local time zone.

See also currentDateTimeUtc(), QDate::currentDate(), QTime::currentTime(), and toTimeSpec().

[static] QDateTime QDateTime::currentDateTimeUtc()

Returns the current datetime, as reported by the system clock, in UTC.

See also currentDateTime(), QDate::currentDate(), QTime::currentTime(), and 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.

See also currentDateTime(), currentDateTimeUtc(), and toTimeSpec().

[static, since 5.8] qint64 QDateTime::currentSecsSinceEpoch()

Returns the number of seconds since 1970-01-01T00:00:00 Universal Coordinated Time.

This function was introduced in Qt 5.8.

See also currentMSecsSinceEpoch().

QDate QDateTime::date() const

Returns the date part of the datetime.

See also setDate(), time(), and timeSpec().

qint64 QDateTime::daysTo(const QDateTime &other) const

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.

If the other datetime is earlier than this datetime, the value returned is negative.

Example:

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);

See also addDays(), secsTo(), and msecsTo().

[static, since 5.5] QDateTime QDateTime::fromCFDate(CFDateRef date)

Constructs a new QDateTime containing a copy of the CFDate date.

This function was introduced in Qt 5.5.

See also toCFDate().

[static] QDateTime QDateTime::fromMSecsSinceEpoch(qint64 msecs, Qt::TimeSpec spec = Qt::LocalTime, 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.

If the spec is not Qt::OffsetFromUTC then the offsetSeconds will be ignored. If the spec is Qt::OffsetFromUTC and the offsetSeconds is 0 then the spec will be set to Qt::UTC, i.e. an offset of 0 seconds.

If spec is Qt::TimeZone then the spec will be set to Qt::LocalTime, i.e. the current system time zone.

See also toMSecsSinceEpoch() and setMSecsSinceEpoch().

[static, since 5.2] 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.

This function was introduced in Qt 5.2.

See also fromSecsSinceEpoch().

[static, since 5.5] QDateTime QDateTime::fromNSDate(const NSDate *date)

Constructs a new QDateTime containing a copy of the NSDate date.

This function was introduced in Qt 5.5.

See also toNSDate().

[static, since 5.8] 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.

If the spec is not Qt::OffsetFromUTC then the offsetSeconds will be ignored. If the spec is Qt::OffsetFromUTC and the offsetSeconds is 0 then the spec will be set to Qt::UTC, i.e. an offset of 0 seconds.

If spec is Qt::TimeZone then the spec will be set to Qt::LocalTime, i.e. the current system time zone.

This function was introduced in Qt 5.8.

See also toSecsSinceEpoch() and setSecsSinceEpoch().

[static, since 5.8] 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.

This function was introduced in Qt 5.8.

See also fromMSecsSinceEpoch().

[static] QDateTime QDateTime::fromString(const QString &string, Qt::DateFormat format = Qt::TextDate)

Returns the QDateTime represented by the string, using the 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.

See also toString() and QLocale::toDateTime().

[static, since 6.0] QDateTime QDateTime::fromString(QStringView string, Qt::DateFormat format = Qt::TextDate)

This is an overloaded function.

This function was introduced in Qt 6.0.

[static, since 6.0] QDateTime QDateTime::fromString(QStringView string, QStringView format, QCalendar cal = QCalendar())

This is an overloaded function.

This function was introduced in Qt 6.0.

[static, since 6.0] QDateTime QDateTime::fromString(const QString &string, QStringView format, QCalendar cal = QCalendar())

This is an overloaded function.

This function was introduced in Qt 6.0.

[static] QDateTime QDateTime::fromString(const QString &string, const QString &format, QCalendar cal = QCalendar())

Returns the QDateTime represented by the string, using the 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() and QTime::fromString(), this method supports:

ExpressionOutput
tthe timezone (for example "CEST")

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() and QTime::fromString().

For example:

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 date-time (e.g. in a gap skipped by a time-zone transition), an invalid QDateTime is returned, whose toMSecsSinceEpoch() represents a near-by date-time that is valid. Passing that to fromMSecsSinceEpoch() will produce a valid date-time 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);

Note: 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().

See also toString(), QDate::fromString(), QTime::fromString(), and QLocale::toDateTime().

[since 5.2] bool QDateTime::isDaylightTime() const

Returns if this datetime falls in Daylight-Saving Time.

If the Qt::TimeSpec is not Qt::LocalTime or Qt::TimeZone then will always return false.

This function was introduced in Qt 5.2.

See also timeSpec().

bool QDateTime::isNull() const

Returns true if both the date and the time are null; otherwise returns false. A null datetime is invalid.

See also QDate::isNull(), QTime::isNull(), and isValid().

bool QDateTime::isValid() const

Returns true if both the date and the time are valid and they are valid in the current Qt::TimeSpec, otherwise returns false.

If the timeSpec() is Qt::LocalTime or Qt::TimeZone and this object represents a time that was skipped by a forward transition, then it is invalid. For example, if DST ends at 2am with the clock advancing to 3am, then date-times from 02:00:00 to 02:59:59.999 on that day are considered invalid.

See also QDateTime::YearRange, QDate::isValid(), and QTime::isValid().

qint64 QDateTime::msecsTo(const QDateTime &other) const

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.

See also addMSecs(), daysTo(), and QTime::msecsTo().

[since 5.2] int QDateTime::offsetFromUtc() const

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. 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).

This function was introduced in Qt 5.2.

See also setOffsetFromUtc().

qint64 QDateTime::secsTo(const QDateTime &other) const

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.

Example:

QDateTime now = QDateTime::currentDateTime();
QDateTime xmas(QDate(now.date().year(), 12, 25).startOfDay());
qDebug("There are %d seconds to Christmas", now.secsTo(xmas));

See also addSecs(), daysTo(), and QTime::secsTo().

void QDateTime::setDate(QDate date)

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.

See also date(), setTime(), and setTimeSpec().

void QDateTime::setMSecsSinceEpoch(qint64 msecs)

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()) to msecs will result in undefined behavior.

See also toMSecsSinceEpoch() and setSecsSinceEpoch().

[since 5.2] void QDateTime::setOffsetFromUtc(int offsetSeconds)

Sets the timeSpec() to 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.

If offsetSeconds is 0 then the timeSpec() will be set to Qt::UTC.

This function was introduced in Qt 5.2.

See also isValid() and offsetFromUtc().

[since 5.8] void QDateTime::setSecsSinceEpoch(qint64 secs)

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.

This function was introduced in Qt 5.8.

See also toSecsSinceEpoch() and setMSecsSinceEpoch().

void QDateTime::setTime(QTime time)

Sets the time part of this datetime to time. If 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());

See also time(), setDate(), and setTimeSpec().

void QDateTime::setTimeSpec(Qt::TimeSpec spec)

Sets the time specification used in this datetime to spec. The datetime will refer to a different point in time.

If spec is Qt::OffsetFromUTC then the timeSpec() will be set to Qt::UTC, i.e. an effective offset of 0.

If spec is Qt::TimeZone then the spec will be set to Qt::LocalTime, i.e. the current system time zone.

Example:

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.";

See also timeSpec(), setDate(), setTime(), setTimeZone(), and Qt::TimeSpec.

[since 5.2] void QDateTime::setTimeZone(const QTimeZone &toZone)

Sets the time zone used in this datetime to toZone. The datetime will refer to a different point in time.

If toZone is invalid then the datetime will be invalid.

This function was introduced in Qt 5.2.

See also timeZone() and Qt::TimeSpec.

[since 5.0] void QDateTime::swap(QDateTime &other)

Swaps this datetime with other. This operation is very fast and never fails.

This function was introduced in Qt 5.0.

QTime QDateTime::time() const

Returns the time part of the datetime.

See also setTime(), date(), and timeSpec().

Qt::TimeSpec QDateTime::timeSpec() const

Returns the time specification of the datetime.

See also setTimeSpec(), date(), time(), and Qt::TimeSpec.

[since 5.2] QTimeZone QDateTime::timeZone() const

Returns the time zone of the datetime.

If the timeSpec() is 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.

This function was introduced in Qt 5.2.

See also setTimeZone() and Qt::TimeSpec.

[since 5.2] QString QDateTime::timeZoneAbbreviation() const

Returns the Time Zone Abbreviation for this datetime.

The returned string depends on timeSpec():

Note: 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.

This function was introduced in Qt 5.2.

See also timeSpec() and QTimeZone::abbreviation().

[since 5.5] CFDateRef QDateTime::toCFDate() const

Creates a CFDate from a QDateTime.

The caller owns the CFDate object and is responsible for releasing it.

This function was introduced in Qt 5.5.

See also fromCFDate().

QDateTime QDateTime::toLocalTime() const

Returns a datetime containing the date and time information in this datetime, but specified using the Qt::LocalTime definition.

Example:

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);

See also toTimeSpec().

qint64 QDateTime::toMSecsSinceEpoch() const

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.

See also toSecsSinceEpoch() and setMSecsSinceEpoch().

[since 5.5] NSDate *QDateTime::toNSDate() const

Creates an NSDate from a QDateTime.

The NSDate object is autoreleased.

This function was introduced in Qt 5.5.

See also fromNSDate().

[since 5.2] QDateTime QDateTime::toOffsetFromUtc(int offsetSeconds) const

Returns a copy of this datetime converted to a spec of Qt::OffsetFromUTC with the given offsetSeconds.

If the offsetSeconds equals 0 then a UTC datetime will be returned

This function was introduced in Qt 5.2.

See also setOffsetFromUtc(), offsetFromUtc(), and toTimeSpec().

[since 5.8] qint64 QDateTime::toSecsSinceEpoch() const

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.

This function was introduced in Qt 5.8.

See also toMSecsSinceEpoch() and setSecsSinceEpoch().

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

This is an overloaded function.

Returns the datetime as a string in the format given.

If the format is Qt::TextDate, the string is formatted in the default way. The day and month names will be in English. An example of this formatting is "Wed May 20 03:40:13 1998". For localized formatting, see QLocale::toString().

If the format is Qt::ISODate, the string format corresponds to the ISO 8601 extended specification for representations of dates and times, taking the form yyyy-MM-ddTHH:mm:ss[Z|[+|-]HH:mm], depending on the timeSpec() of the QDateTime. If the timeSpec() is Qt::UTC, Z will be appended to the string; if the timeSpec() is 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].

If the format is Qt::RFC2822Date, the string is formatted following RFC 2822.

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

Warning: The Qt::ISODate format is only valid for years in the range 0 to 9999.

See also fromString(), QDate::toString(), QTime::toString(), and QLocale::toString().

QDateTime QDateTime::toTimeSpec(Qt::TimeSpec spec) const

Returns a copy of this datetime converted to the given time spec.

If spec is Qt::OffsetFromUTC then it is set to Qt::UTC. To set to a spec of Qt::OffsetFromUTC use toOffsetFromUtc().

If spec is Qt::TimeZone then it is set to Qt::LocalTime, i.e. the local Time Zone.

Example:

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);

See also timeSpec(), toTimeZone(), and toOffsetFromUtc().

[since 5.2] QDateTime QDateTime::toTimeZone(const QTimeZone &timeZone) const

Returns a copy of this datetime converted to the given timeZone

This function was introduced in Qt 5.2.

See also timeZone() and toTimeSpec().

QDateTime QDateTime::toUTC() const

Returns a datetime containing the date and time information in this datetime, but specified using the Qt::UTC definition.

Example:

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);

See also toTimeSpec().

Related Non-Members

bool operator!=(const QDateTime &lhs, const QDateTime &rhs)

Returns true if lhs is different from rhs; otherwise returns 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).

See also operator==().

bool operator<(const QDateTime &lhs, const QDateTime &rhs)

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

See also operator==().

QDataStream &operator<<(QDataStream &out, const QDateTime &dateTime)

Writes dateTime to the out stream.

See also Serializing Qt Data Types.

bool operator<=(const QDateTime &lhs, const QDateTime &rhs)

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

See also operator==().

bool operator==(const QDateTime &lhs, const QDateTime &rhs)

Returns true if lhs is the same as rhs; otherwise returns 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).

See also operator!=(), operator<(), operator<=(), operator>(), and operator>=().

bool operator>(const QDateTime &lhs, const QDateTime &rhs)

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

See also operator==().

bool operator>=(const QDateTime &lhs, const QDateTime &rhs)

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

See also operator==().

QDataStream &operator>>(QDataStream &in, QDateTime &dateTime)

Reads a datetime from the stream in into dateTime.

See also Serializing Qt Data Types.

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