Qt 4.8: QTime Class Reference

Qt Reference Documentation

- Qt 4.8
- ALL VERSIONS

- A
- A
- A
- Print

# QTime Class Reference

The QTime class provides clock time functions. More...

     #include <QTime>

Note: All functions in this class are reentrant.

- List of all members, including inherited members
- Qt 3 support members

## Public Functions

| QTime ()
| QTime ( int h, int m, int s = 0, int ms = 0 )
QTime | addMSecs ( int ms ) const
QTime | addSecs ( int s ) const
int | elapsed () const
int | hour () const
bool | isNull () const
bool | isValid () const
int | minute () const
int | msec () const
int | msecsTo ( const QTime & t ) const
int | restart ()
int | second () const
int | secsTo ( const QTime & t ) const
bool | setHMS ( int h, int m, int s, int ms = 0 )
void | start ()
QString | toString ( const QString & format ) const
QString | toString ( Qt::DateFormat format = Qt::TextDate ) const
bool | operator!= ( const QTime & t ) const
bool | operator< ( const QTime & t ) const
bool | operator<= ( const QTime & t ) const
bool | operator== ( const QTime & t ) const
bool | operator> ( const QTime & t ) const
bool | operator>= ( const QTime & t ) const

## Static Public Members

QTime | currentTime ()
QTime | fromString ( const QString & string, Qt::DateFormat format = Qt::TextDate )
QTime | fromString ( const QString & string, const QString & format )
bool | isValid ( int h, int m, int s, int ms = 0 )

## Related Non-Members

QDataStream & | operator<< ( QDataStream & out, const QTime & time )
QDataStream & | operator>> ( QDataStream & in, QTime & time )

## Detailed Description

The QTime class provides clock time functions.

A QTime object contains a clock time, i.e. the number of hours, minutes, seconds, and milliseconds since midnight. It can read the current time from the system clock and measure a span of elapsed time. It provides functions for comparing times and for manipulating a time by adding a number of milliseconds.

QTime uses the 24-hour clock format; it has no concept of AM/PM. Unlike QDateTime, QTime knows nothing about time zones or daylight savings time (DST).

A QTime object is typically created either by giving the number of hours, minutes, seconds, and milliseconds explicitly, or by using the static function currentTime(), which creates a QTime object that contains the system's local time. Note that the accuracy depends on the accuracy of the underlying operating system; not all systems provide 1-millisecond accuracy.

The hour(), minute(), second(), and msec() functions provide access to the number of hours, minutes, seconds, and milliseconds of the time. The same information is provided in textual format by the toString() function.

QTime provides a full set of operators to compare two QTime objects. One time is considered smaller than another if it is earlier than the other.

The time a given number of seconds or milliseconds later than a given time can be found using the addSecs() or addMSecs() functions. Correspondingly, the number of seconds or milliseconds between two times can be found using secsTo() or msecsTo().

QTime can be used to measure a span of elapsed time using the start(), restart(), and elapsed() functions.

See also QDate and QDateTime.

## Member Function Documentation

### QTime::QTime ()

Constructs a null time object. A null time can be a QTime(0, 0, 0, 0) (i.e., midnight) object, except that isNull() returns true and isValid() returns false.

See also isNull() and isValid().

### QTime::QTime ( int h, int m, int s = 0, int ms = 0 )

Constructs a time with hour h, minute m, seconds s and milliseconds ms.

h must be in the range 0 to 23, m and s must be in the range 0 to 59, and ms must be in the range 0 to 999.

See also isValid().

### QTime QTime::addMSecs ( int ms ) const

Returns a QTime object containing a time ms milliseconds later than the time of this object (or earlier if ms is negative).

Note that the time will wrap if it passes midnight. See addSecs() for an example.

See also addSecs(), msecsTo(), and QDateTime::addMSecs().

### QTime QTime::addSecs ( int s ) const

Returns a QTime object containing a time s seconds later than the time of this object (or earlier if s is negative).

Note that the time will wrap if it passes midnight.

Example:

     QTime n(14, 0, 0);                // n == 14:00:00
     QTime t;
     t = n.addSecs(70);                // t == 14:01:10
     t = n.addSecs(-70);               // t == 13:58:50
     t = n.addSecs(10 * 60 * 60 + 5);  // t == 00:00:05
     t = n.addSecs(-15 * 60 * 60);     // t == 23:00:00

See also addMSecs(), secsTo(), and QDateTime::addSecs().

### QTime QTime::currentTime ()`[static]`

Returns the current time as reported by the system clock.

Note that the accuracy depends on the accuracy of the underlying operating system; not all systems provide 1-millisecond accuracy.

### int QTime::elapsed () const

Returns the number of milliseconds that have elapsed since the last time start() or restart() was called.

Note that the counter wraps to zero 24 hours after the last call to start() or restart.

Note that the accuracy depends on the accuracy of the underlying operating system; not all systems provide 1-millisecond accuracy.

Warning: If the system's clock setting has been changed since the last time start() or restart() was called, the result is undefined. This can happen when daylight savings time is turned on or off.

See also start() and restart().

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

Returns the time represented in the string as a QTime using the format given, or an invalid time if this is not possible.

Note that fromString() uses a "C" locale encoded string to convert milliseconds to a float value. If the default locale is not "C", this may result in two conversion attempts (if the conversion fails for the default locale). This should be considered an implementation detail.

### QTime QTime::fromString ( const QString & string, const QString & format )`[static]`

Returns the QTime represented by the string, using the format given, or an invalid time if the string cannot be parsed.

These expressions may be used for the format:

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 without a leading zero (0 to 59)
ss | the second with 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 | interpret as an AM/PM time. AP must be either "AM" or "PM".
ap | Interpret as an AM/PM time. ap must be either "am" or "pm".

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

     QTime time = QTime::fromString("1mm12car00", "m'mm'hcarss");
     // time is 12:01.00

If the format is not satisfied an invalid QTime is returned. Expressions that do not expect leading zeroes to be given (h, m, s and z) are greedy. This means that they will use two digits even if this puts them outside the range of accepted values and leaves too few digits for other sections. For example, the following string could have meant 00:07:10, but the m will grab two digits, resulting in an invalid time:

     QTime time = QTime::fromString("00:710", "hh:ms"); // invalid

Any field that is not represented in the format will be set to zero. For example:

     QTime time = QTime::fromString("1.30", "m.s");
     // time is 00:01:30.000

QDateTime::toString() QTime::toString()

See also QDateTime::fromString(), QDate::fromString(), and QDate::toString().

### int QTime::hour () const

Returns the hour part (0 to 23) of the time.

See also minute(), second(), and msec().

### bool QTime::isNull () const

Returns true if the time is null (i.e., the QTime object was constructed using the default constructor); otherwise returns false. A null time is also an invalid time.

See also isValid().

### bool QTime::isValid () const

Returns true if the time is valid; otherwise returns false. For example, the time 23:30:55.746 is valid, but 24:12:30 is invalid.

See also isNull().

### bool QTime::isValid ( int h, int m, int s, int ms = 0 )`[static]`

This is an overloaded function.

Returns true if the specified time is valid; otherwise returns false.

The time is valid if h is in the range 0 to 23, m and s are in the range 0 to 59, and ms is in the range 0 to 999.

Example:

     QTime::isValid(21, 10, 30); // returns true
     QTime::isValid(22, 5,  62); // returns false

### int QTime::minute () const

Returns the minute part (0 to 59) of the time.

See also hour(), second(), and msec().

### int QTime::msec () const

Returns the millisecond part (0 to 999) of the time.

See also hour(), minute(), and second().

### int QTime::msecsTo ( const QTime & t ) const

Returns the number of milliseconds from this time to t. If t is earlier than this time, the number of milliseconds returned is negative.

Because QTime measures time within a day and there are 86400 seconds in a day, the result is always between -86400000 and 86400000 ms.

See also secsTo(), addMSecs(), and QDateTime::msecsTo().

### int QTime::restart ()

Sets this time to the current time and returns the number of milliseconds that have elapsed since the last time start() or restart() was called.

This function is guaranteed to be atomic and is thus very handy for repeated measurements. Call start() to start the first measurement, and restart() for each later measurement.

Note that the counter wraps to zero 24 hours after the last call to start() or restart().

Warning: If the system's clock setting has been changed since the last time start() or restart() was called, the result is undefined. This can happen when daylight savings time is turned on or off.

See also start(), elapsed(), and currentTime().

### int QTime::second () const

Returns the second part (0 to 59) of the time.

See also hour(), minute(), and msec().

### int QTime::secsTo ( const QTime & t ) const

Returns the number of seconds from this time to t. If t is earlier than this time, the number of seconds returned is negative.

Because QTime measures time within a day and there are 86400 seconds in a day, the result is always between -86400 and 86400.

secsTo() does not take into account any milliseconds.

See also addSecs() and QDateTime::secsTo().

### bool QTime::setHMS ( int h, int m, int s, int ms = 0 )

Sets the time to hour h, minute m, seconds s and milliseconds ms.

h must be in the range 0 to 23, m and s must be in the range 0 to 59, and ms must be in the range 0 to 999. Returns true if the set time is valid; otherwise returns false.

See also isValid().

### void QTime::start ()

Sets this time to the current time. This is practical for timing:

     QTime t;
     t.start();
     some_lengthy_task();
     qDebug("Time elapsed: %d ms", t.elapsed());

See also restart(), elapsed(), and currentTime().

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

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

These expressions may be used:

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)
H | the hour without a leading zero (0 to 23, even with AM/PM display)
HH | the hour with a leading zero (00 to 23, even with 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 without a leading zero (0 to 59)
ss | the second with 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 or A | use AM/PM display. AP will be replaced by either "AM" or "PM".
ap or a | use am/pm display. ap will be replaced by either "am" or "pm".
t | the timezone (for example "CEST")

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. Two consecutive singlequotes ("''") are replaced by a singlequote in the output.

Example format strings (assuming that the QTime is 14:13:09.042)

Format | Result
--- | ---
hh:mm:ss.zzz | 14:13:09.042
h:m:s ap | 2:13:9 pm
H:m:s a | 14:13:9 pm

If the datetime is invalid, an empty string will be returned. If format is empty, the default format "hh:mm:ss" is used.

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

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

This is an overloaded function.

Returns the time as a string. Milliseconds are not included. The format parameter determines the format of the string.

If format is Qt::TextDate, the string format is HH:MM:SS; e.g. 1 second before midnight would be "23:59:59".

If format is Qt::ISODate, the string format corresponds to the ISO 8601 extended specification for representations of dates, which is also HH:mm:ss. (However, contrary to ISO 8601, dates before 15 October 1582 are handled as Julian dates, not Gregorian dates. See Use of Gregorian and Julian Calendars. This might change in a future version of Qt.)

If the format is Qt::SystemLocaleShortDate or Qt::SystemLocaleLongDate, the string format depends on the locale settings of the system. Identical to calling QLocale::system().toString(time, QLocale::ShortFormat) or QLocale::system().toString(time, QLocale::LongFormat).

If the format is Qt::DefaultLocaleShortDate or Qt::DefaultLocaleLongDate, the string format depends on the default application locale. This is the locale set with QLocale::setDefault(), or the system locale if no default locale has been set. Identical to calling QLocale().toString(time, QLocale::ShortFormat) or QLocale().toString(time, QLocale::LongFormat).

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

### bool QTime::operator!= ( const QTime & t ) const

Returns true if this time is different from t; otherwise returns false.

### bool QTime::operator< ( const QTime & t ) const

Returns true if this time is earlier than t; otherwise returns false.

### bool QTime::operator<= ( const QTime & t ) const

Returns true if this time is earlier than or equal to t; otherwise returns false.

### bool QTime::operator== ( const QTime & t ) const

Returns true if this time is equal to t; otherwise returns false.

### bool QTime::operator> ( const QTime & t ) const

Returns true if this time is later than t; otherwise returns false.

### bool QTime::operator>= ( const QTime & t ) const

Returns true if this time is later than or equal to t; otherwise returns false.

## Related Non-Members

### QDataStream & operator<< ( QDataStream & out, const QTime & time )

Writes time to stream out.

See also Serializing Qt Data Types.

### QDataStream & operator>> ( QDataStream & in, QTime & time )

Reads a time from stream in into the given time.

See also Serializing Qt Data Types.