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# QDateTime Class Reference

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

`#include <qdatetime.h>`

List of all member functions.

## Public Members

- QDateTime ()
- QDateTime ( const QDate & )
- QDateTime ( const QDate &, const QTime & )
- bool isNull () const
- bool isValid () const
- QDate date () const
- QTime time () const
- void setDate ( const QDate & date )
- void setTime ( const QTime & time )
- void setTime_t ( uint secsSince1Jan1970UTC )
- QString toString () const
- QDateTime addDays ( int days ) const
- QDateTime addSecs ( int secs ) const
- int daysTo ( const QDateTime & ) const
- int secsTo ( const QDateTime & ) const
- bool operator== ( const QDateTime & dt ) const
- bool operator!= ( const QDateTime & dt ) const
- bool operator< ( const QDateTime & dt ) const
- bool operator<= ( const QDateTime & dt ) const
- bool operator> ( const QDateTime & dt ) const
- bool operator>= ( const QDateTime & dt ) const

## Static Public Members

- QDateTime currentDateTime ()

## Related Functions

(Note that these are not member functions.)

- QDataStream & operator<< (QDataStream & s, const QDateTime & dt)
- QDataStream & operator>> (QDataStream & s, QDateTime & dt)

## 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 or days.

A QDateTime object is typically created either by giving a date and time explicitly, or by using the static function currentTime(), which makes a QDateTime object which contains the system's clock time.

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. A datetime is considered smaller than another if it is earlier than the other.

The datetime a given number of days or seconds later than a given datetime can be found using the addDays() and addSecs() functions. Correspondingly, the number of days or seconds between two times can be found using the daysTo() or secsTo() functions.

A datetime can also be set using the setTime_t() function, which takes a POSIX-standard "number of seconds since 00:00:00 on January 1, 1970" value.

The limitations regarding range and resolution mentioned in the QDate and QTime documentation apply for QDateTime also.

See also QDate and QTime.

## 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 date date and null time (00:00:00.000).

### QDateTime::QDateTime ( const QDate & date, const QTime & time )

Constructs a datetime with date date and time time.

### 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() 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() and addDays().

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

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

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

### QDate QDateTime::date () const

Returns the date part of this datetime.

See also setDate() and time().

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

Returns the number of days from this datetime to dt (which is negative if dt is earlier than this datetime).

See also addDays() and secsTo().

### bool QDateTime::isNull () const

Returns TRUE if both the date and the time are null. A null date is invalid.

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

### bool QDateTime::isValid () const

Returns TRUE if both the date and the time are valid.

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

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

Returns TRUE if this datetime is different from dt, or FALSE if they are equal.

See also operator==().

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

Returns TRUE if this datetime is earlier than dt, otherwise FALSE.

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

Returns TRUE if this datetime is earlier than or equal to dt, otherwise FALSE.

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

Returns TRUE if this datetime is equal to dt, or FALSE if they are different.

See also operator!=().

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

Returns TRUE if this datetime is later than dt, otherwise FALSE.

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

Returns TRUE if this datetime is later than or equal to dt, otherwise FALSE.

### int QDateTime::secsTo ( const QDateTime & dt ) const

Returns the number of seconds from this datetime to dt (which is negative if dt is earlier than this datetime).

Example:

        QDateTime dt = QDateTime::currentDateTime();
        QDateTime x( QDate(dt.year(),12,24), QTime(17,00) );
        qDebug( "There are %d seconds to Christmas", dt.secsTo(x) );

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

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

Sets the date part of this datetime.

See also date() and setTime().

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

Sets the time part of this datetime.

See also time() and setDate().

### void QDateTime::setTime_t ( uint secsSince1Jan1970UTC )

Sets the local date and time given the number of seconds that have passed since 00:00:00 on January 1, 1970, Coordinated Universal Time (UTC). On systems that do not support timezones this function will behave as if local time were UTC.

Note that Microsoft Windows supports only a limited range of values for secsSince1Jan1970UTC.

### QTime QDateTime::time () const

Returns the time part of this datetime.

See also setTime() and date().

### QString QDateTime::toString () const

Returns the datetime as a string.

The string format is "Sat May 20 03:40:13 1998".

This function uses QDate::dayName(), QDate::monthName(), and QTime::toString() to generate the string.

## Related Functions

### QDataStream & operator<< (QDataStream & s, const QDateTime & dt)

Writes a datetime to the stream.

See also Format of the QDataStream operators

### QDataStream & operator>> (QDataStream & s, QDateTime & dt)

Reads a datetime from the stream.

See also Format of the QDataStream operators

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