QTime Class

Member Function Documentation

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

These expressions may be used:

Any non-empty 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 (assuming that the QTime is 14:13:09.042 and the system locale is en_US)

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

Note: If localized forms of am or pm (the AP, ap, A or a formats) are desired, please switch to using QLocale::system().toString() as QTime methods shall change to use English (C locale) at Qt 6.

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

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()

Constructs a null time object. For a null time, isNull() returns true and isValid() returns false. If you need a zero time, use QTime(0, 0). For the start of a day, see QDate::startOfDay().

See also isNull() and 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.

Returns a null time if this time is invalid.

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.

Returns a null time if this time is invalid.

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().

[static] QTime QTime::currentTime()

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.

Furthermore, currentTime() only increases within each day; it shall drop by 24 hours each time midnight passes; and, beside this, changes in it may not correspond to elapsed time, if a daylight-saving transition intervenes.

See also QDateTime::currentDateTime() and QDateTime::currentDateTimeUtc().

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-saving time is turned on or off.

See also start() and restart().

[static] QTime QTime::fromMSecsSinceStartOfDay(int msecs)

Returns a new QTime instance with the time set to the number of msecs since the start of the day, i.e. since 00:00:00.

If msecs falls outside the valid range an invalid QTime will be returned.

See also msecsSinceStartOfDay().

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

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.

Note: Support for localized dates, including the format options Qt::SystemLocaleDate, Qt::SystemLocaleShortDate, Qt::SystemLocaleLongDate, Qt::LocaleDate, Qt::DefaultLocaleShortDate, and Qt::DefaultLocaleLongDate, shall be removed in Qt 6. Use QLocale::toTime() instead.

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

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

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:

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 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

Note: If localized forms of am or pm (the AP, ap, A or a formats) are used, please switch to using QLocale::system().toTime() as QTime methods shall change to only recognize English (C locale) at Qt 6.

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

int QTime::hour() const

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

Returns -1 if the time is invalid.

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().

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

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.

Returns -1 if the time is invalid.

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

int QTime::msec() const

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

Returns -1 if the time is invalid.

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

int QTime::msecsSinceStartOfDay() const

Returns the number of msecs since the start of the day, i.e. since 00:00:00.

See also fromMSecsSinceStartOfDay().

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.

Returns 0 if either time is invalid.

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-saving 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.

Returns -1 if the time is invalid.

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.

Returns 0 if either time is invalid.

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(Qt::DateFormat format = Qt::TextDate) const

This is an overloaded function.

Returns the time as a string. 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, represented by HH:mm:ss. To include milliseconds in the ISO 8601 date, use the format Qt::ISODateWithMs, which corresponds to HH:mm:ss.zzz.

The format options Qt::SystemLocaleDate:, Qt::SystemLocaleShortDate and Qt::SystemLocaleLongDate shall be removed in Qt 6. Their use should be replaced with: QLocale::system().toString(time, QLocale::ShortFormat) or QLocale::system().toString(time, QLocale::LongFormat).

The format options Qt::LocaleDate, Qt::DefaultLocaleShortDate and Qt::DefaultLocaleLongDate shall be removed in Qt 6. Their use should be replaced with: QLocale().toString(time, QLocale::ShortFormat) or QLocale().toString(time, QLocale::LongFormat).

If the format is Qt::RFC2822Date, the string is formatted in an RFC 2822 compatible way. An example of this formatting is "23:59:20".

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

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

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.