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# QDateTime Class Reference

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

    #include <QDateTime>

Note: All the functions in this class are reentrant.

- List of all members, including inherited members
- Compatibility members

### Public Functions

- QDateTime ()
- QDateTime ( const QDate & date )
- QDateTime ( const QDate & date, const QTime & time, Qt::TimeSpec spec = Qt::LocalTime )
- QDateTime ( const QDateTime & other )
- ~QDateTime ()
- QDateTime addDays ( int ndays ) const
- QDateTime addMonths ( int nmonths ) const
- QDateTime addSecs ( int nsecs ) const
- QDateTime addYears ( int nyears ) const
- QDate date () const
- int daysTo ( const QDateTime & other ) const
- bool isNull () const
- bool isValid () const
- int secsTo ( const QDateTime & other ) const
- void setDate ( const QDate & date )
- void setTime ( const QTime & time )
- void setTimeSpec ( Qt::TimeSpec spec )
- void setTime_t ( uint seconds )
- QTime time () const
- Qt::TimeSpec timeSpec () const
- QDateTime toLocalTime () const
- QString toString ( const QString & format ) const
- QString toString ( Qt::DateFormat format = Qt::TextDate ) const
- QDateTime toTimeSpec ( Qt::TimeSpec specification ) const
- uint toTime_t () const
- QDateTime toUTC () const
- bool operator!= ( const QDateTime & other ) const
- bool operator< ( const QDateTime & other ) const
- bool operator<= ( const QDateTime & other ) const
- QDateTime & operator= ( const QDateTime & other )
- bool operator== ( const QDateTime & other ) const
- bool operator> ( const QDateTime & other ) const
- bool operator>= ( const QDateTime & other ) const

### Static Public Members

- QDateTime currentDateTime ()
- QDateTime fromString ( const QString & string, Qt::DateFormat format = Qt::TextDate )

### Related Non-Members

- QDataStream & operator<< ( QDataStream & stream, const QDateTime & datetime )
- QDataStream & operator>> ( QDataStream & stream, QDateTime & datetime )

## Detailed Description

The QDateTime class provides date and time functions.

A QDateTime object contains a calendar date and a clock time (a "datetime"). It is a combination 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.

A QDateTime object is typically created either by giving a date and time explicitly in the constructor, or by using the static function currentDateTime() that returns a QDateTime object set to the system clock's time. The date and time can be changed with setDate() and setTime(). A datetime can also be set using the setTime_t() function that takes a POSIX-standard "number of seconds since 00:00:00 on January 1, 1970" value. The fromString() function returns a QDateTime, given a string and a date format used to interpret the date within the string.

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 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, and secsTo() returns the number of seconds between two datetimes.

The range of a datetime object is constrained to the ranges of the QDate and QTime objects which it encapsulates.

See also QDate, QTime, and QDateTimeEdit.

## Member Function Documentation

### QDateTime::QDateTime ()

Constructs a null datetime (i.e. null date and null time). A null datetime is invalid, since the date is invalid.

See also isValid().

### QDateTime::QDateTime ( const QDate & date )

Constructs a datetime with the given date, and a null but valid time (00:00:00.000).

### QDateTime::QDateTime ( const QDate & date, const QTime & time, Qt::TimeSpec spec = Qt::LocalTime )

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

### QDateTime::QDateTime ( const QDateTime & other )

Constructs a copy of the other datetime.

### QDateTime::~QDateTime ()

Destroys the datetime.

### QDateTime QDateTime::addDays ( int ndays ) const

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

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

### 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).

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

### QDateTime QDateTime::addSecs ( int nsecs ) const

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

See also 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).

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

### QDateTime QDateTime::currentDateTime () `[static]`

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

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

### QDate QDateTime::date () const

Returns the date part of the datetime.

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

### int QDateTime::daysTo ( const QDateTime & other ) const

Returns the number of days from this datetime to the other datetime. If the other datetime is earlier than this datetime, the value returned is negative.

See also addDays() and secsTo().

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

Returns the QDateTime represented by the string, using the 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, they depend on the user's locale settings.

Warning: Note that `Qt::LocalDate` cannot be used here.

### 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; otherwise returns false.

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

### int 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.

Example:

        QDateTime dt = QDateTime();
        QDateTime xmas(QDate(dt.date().year(), 12, 25), QTime(17, 00));
        qDebug("There are %d seconds to Christmas", dt.secsTo(xmas));

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

### void QDateTime::setDate ( const QDate & date )

Sets the date part of this datetime to date.

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

### void QDateTime::setTime ( const QTime & time )

Sets the time part of this datetime to time.

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

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

Sets the time specification used in this datetime to spec.

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

### void QDateTime::setTime_t ( uint seconds )

Sets the date and time given the number of seconds that have passed since 1970-01-01T00:00:00, Coordinated Universal Time (Qt::UTC). On systems that do not support timezones this function will behave as if local time were Qt::UTC.

See also toTime_t().

### QTime QDateTime::time () const

Returns the time part of the datetime.

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

### Qt::TimeSpec QDateTime::timeSpec () const

Returns the time specification of the datetime.

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

### QDateTime QDateTime::toLocalTime () const

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

See also Qt::TimeSpec.

### QString QDateTime::toString ( const QString & format ) const

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

These expressions may be used for the date:

Expression | Output
--- | ---
d | the day as number without a leading zero (1 to 31)
dd | the day as number with a leading zero (01 to 31)
ddd | the abbreviated localized day name (e.g. 'Mon' to 'Sun'). Uses QDate::shortDayName().
dddd | the long localized day name (e.g. 'Qt::Monday' to 'Qt::Sunday'). Uses QDate::longDayName().
M | the month as number without a leading zero (1-12)
MM | the month as number with a leading zero (01-12)
MMM | the abbreviated localized month name (e.g. 'Jan' to 'Dec'). Uses QDate::shortMonthName().
MMMM | the long localized month name (e.g. 'January' to 'December'). Uses QDate::longMonthName().
yy | the year as two digit number (00-99)
yyyy | the year as four digit number (1752-8000)

These expressions may be used for the time:

Expression | Output
--- | ---
h | the hour without a leading zero (0 to 23 or 1 to 12 if AM/PM display)
hh | the hour with a leading zero (00 to 23 or 01 to 12 if AM/PM display)
m | the minute without a leading zero (0 to 59)
mm | the minute with a leading zero (00 to 59)
s | the second whithout a leading zero (0 to 59)
ss | the second whith a leading zero (00 to 59)
z | the milliseconds without leading zeroes (0 to 999)
zzz | the milliseconds with leading zeroes (000 to 999)
AP | use AM/PM display. AP will be replaced by either "AM" or "PM".
ap | use am/pm display. ap will be replaced by either "am" or "pm".

All other input characters will be ignored. Any sequence of characters that are enclosed in singlequotes will be treated as text and not be used as an expression.

Example format strings (assumed that the QDateTime is 21<small><sup>st</sup></small> May 2001 14:13:09)

Format | Result
--- | ---
dd.MM.yyyy | 21.05.2001
ddd MMMM d yy | Tue May 21 01
hh:mm:ss.zzz | 14:13:09.042
h:m:s ap | 2:13:9 pm

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

See also QDate::toString() and QTime::toString().

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above 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. QDate::shortDayName(), QDate::shortMonthName(), and QTime::toString() are used to generate the string, so the day and month names will be localized names. An example of this formatting is "Wed May 20 03:40:13 1998".

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.

If the format is `Qt::LocalDate`, the string format depends on the locale settings of the system.

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

See also QDate::toString(), QTime::toString(), and Qt::DateFormat.

### QDateTime QDateTime::toTimeSpec ( Qt::TimeSpec specification ) const

Returns a copy of this datetime configured to use the given time specification.

### uint QDateTime::toTime_t () const

Returns the datetime as the number of seconds that have passed since 1970-01-01T00:00:00, Coordinated Universal Time (Qt::UTC).

On systems that do not support timezones, this function will behave as if local time were `Qt::UTC`.

See also setTime_t().

### QDateTime QDateTime::toUTC () const

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

See also Qt::TimeSpec.

### bool QDateTime::operator!= ( const QDateTime & other ) const

Returns 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.

See also operator==().

### bool QDateTime::operator< ( const QDateTime & other ) const

Returns true if this datetime is earlier than the other datetime; otherwise returns false.

### bool QDateTime::operator<= ( const QDateTime & other ) const

Returns true if this datetime is earlier than or equal to the other datetime; otherwise returns false.

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

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

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

Returns true if this datetime is equal to the other datetime; otherwise returns false.

See also operator!=().

### bool QDateTime::operator> ( const QDateTime & other ) const

Returns true if this datetime is later than the other datetime; otherwise returns false.

### bool QDateTime::operator>= ( const QDateTime & other ) const

Returns true if this datetime is later than or equal to the other datetime; otherwise returns false.

## Related Non-Members

### QDataStream & operator<< ( QDataStream & stream, const QDateTime & datetime )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Writes the datetime to the given stream.

See also Format of the QDataStream operators.

### QDataStream & operator>> ( QDataStream & stream, QDateTime & datetime )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Reads a datetime from the stream into the given datetime.

See also Format of the QDataStream operators.