com.trolltech.qt.core
Class QDateTime

java.lang.Object
  extended by com.trolltech.qt.internal.QSignalEmitterInternal
      extended by com.trolltech.qt.QSignalEmitter
          extended by com.trolltech.qt.QtJambiObject
              extended by com.trolltech.qt.core.QDateTime
All Implemented Interfaces:
QtJambiInterface, java.lang.Cloneable, java.lang.Comparable

public class QDateTime
extends QtJambiObject
implements java.lang.Comparable, java.lang.Cloneable

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.

QDateTime can store datetimes as local time or as UTC . QDateTime::currentDateTime() returns a QDateTime expressed as local time; use toUTC() to convert it to UTC. You can also use timeSpec() to find out if a QDateTime object stores a UTC time or a local time. Operations such as addSecs() and secsTo() are aware of daylight saving time (DST).

Note:QDateTime does not account for leap seconds.

Use of Gregorian and Julian Calendars

QDate uses the Gregorian calendar in all locales, beginning on the date 15 October 1582. For dates up to and including 4 October 1582, the Julian calendar is used. This means there is a 10-day gap in the internal calendar between the 4th and the 15th of October 1582. When you use QDateTime for dates in that epoch, the day after 4 October 1582 is 15 October 1582, and the dates in the gap are invalid.

The Julian to Gregorian changeover date used here is the date when the Gregorian calendar was first introduced, by Pope Gregory XIII. That change was not universally accepted and some localities only executed it at a later date (if at all). QDateTime doesn't take any of these historical facts into account. If an application must support a locale-specific dating system, it must do so on its own, remembering to convert the dates using the Julian day.

No Year 0

There is no year 0. Dates in that year are considered invalid. The year -1 is the year "1 before Christ" or "1 before current era." The day before 0001-01-01 is December 31st, 1 BCE.

Range of Valid Dates

The range of valid dates is from January 2nd, 4713 BCE, to sometime in the year 11 million CE. The Julian Day returned by
QDate::toJulianDay() is a number in the contiguous range from 1 to overflow, even across QDateTime's "date holes". It is suitable for use in applications that must convert a QDateTime to a date in another calendar system, e.g., Hebrew, Islamic or Chinese.

The Gregorian calendar was introduced in different places around the world on different dates. QDateTime uses QDate to store the date, so it uses the Gregorian calendar for all locales, beginning on the date 15 October 1582. For dates up to and including 4 October 1582, QDateTime uses the Julian calendar. This means there is a 10-day gap in the QDateTime calendar between the 4th and the 15th of October 1582. When you use QDateTime for dates in that epoch, the day after 4 October 1582 is 15 October 1582, and the dates in the gap are invalid.

Use of System Timezone

QDateTime uses the system's time zone information to determine the offset of local time from UTC. If the system is not configured correctly or not up-to-date, QDateTime will give wrong results as well.

Daylight Savings Time (DST)

QDateTime takes into account the system's time zone information when dealing with DST. On modern Unix systems, this means it applies the correct historical DST data whenever possible. On Windows and Windows CE, where the system doesn't support historical DST data, historical accuracy is not maintained with respect to DST.

The range of valid dates taking DST into account is 1970-01-01 to the present, and rules are in place for handling DST correctly until 2037-12-31, but these could change. For dates falling outside that range, QDateTime makes a best guess using the rules for year 1970 or 2037, but we can't guarantee accuracy. This means QDateTime doesn't take into account changes in a locale's time zone before 1970, even if the system's time zone database supports that information.

See also:
QDate, QTime, and QDateTimeEdit.


Nested Class Summary
 
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
QSignalEmitter.AbstractSignal, QSignalEmitter.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9
 
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal
 
Field Summary
 
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
currentSender
 
Constructor Summary
QDateTime()
          Constructs a null datetime (i.
QDateTime(QDate arg__1)
          Constructs a datetime with the given date, a valid time(00.00:00.
QDateTime(QDate arg__1, QTime arg__2)
          Constructs a datetime with the given date and time, using the time specification defined by spec.
QDateTime(QDate arg__1, QTime arg__2, Qt.TimeSpec spec)
          Constructs a datetime with the given date and time, using the time specification defined by spec.
QDateTime(QDateTime other)
          Constructs a copy of the other datetime.
 
Method Summary
 QDateTime addDays(int days)
          Returns a QDateTime object containing a datetime ndays days later than the datetime of this object (or earlier if ndays is negative).
 QDateTime addMonths(int months)
          Returns a QDateTime object containing a datetime nmonths months later than the datetime of this object (or earlier if nmonths is negative).
 QDateTime addMSecs(long msecs)
          Returns a QDateTime object containing a datetime msecs miliseconds later than the datetime of this object (or earlier if msecs is negative).
 QDateTime addSecs(int secs)
          Returns a QDateTime object containing a datetime s seconds later than the datetime of this object (or earlier if s is negative).
 QDateTime addYears(int years)
          Returns a QDateTime object containing a datetime nyears years later than the datetime of this object (or earlier if nyears is negative).
 QDateTime clone()
          This method is reimplemented for internal reasons
static QDateTime currentDateTime()
          Returns the current datetime, as reported by the system clock, in the local time zone.
 QDate date()
          Returns the date part of the datetime.
 int daysTo(QDateTime arg__1)
          Returns the number of days from this datetime to the other datetime.
static QDateTime fromString(java.lang.String s)
          Returns the QDateTime represented by the string, using the format given, or an invalid datetime if this is not possible.
static QDateTime fromString(java.lang.String s, Qt.DateFormat f)
          Returns the QDateTime represented by the string, using the format given, or an invalid datetime if this is not possible.
static QDateTime fromString(java.lang.String s, java.lang.String format)
          Returns the QDateTime represented by the string, using the format given, or an invalid datetime if the string cannot be parsed.
static QDateTime fromTime_t(int secsSince1Jan1970UTC)
          Returns a datetime whose date and time are the number of seconds that have passed since 1970-01-01T00.00:00, Coordinated Universal Time (Qt::UTC ).
 boolean isNull()
          Returns true if both the date and the time are null; otherwise returns false.
 boolean isValid()
          Returns true if both the date and the time are valid; otherwise returns false.
 void readFrom(QDataStream arg__1)
          Reads a QDateTime
 int secsTo(QDateTime arg__1)
          Returns the number of seconds from this datetime to the other datetime.
 void setDate(QDate date)
          Sets the date part of this datetime to date.
 void setTime_t(int secsSince1Jan1970UTC)
          Sets the date and time given the number of seconds that have passed since 1970-01-01T00.00:00, Coordinated Universal Time (Qt::UTC ).
 void setTime(QTime time)
          Sets the time part of this datetime to time.
 void setTimeSpec(Qt.TimeSpec spec)
          Sets the time specification used in this datetime to spec.
 QTime time()
          Returns the time part of the datetime.
 Qt.TimeSpec timeSpec()
          Returns the time specification of the datetime.
 QDateTime toLocalTime()
          Returns a datetime containing the date and time information in this datetime, but specified using the Qt::LocalTime definition.
 java.lang.String toString()
          Returns a string representation of the this QDateTime.
 java.lang.String toString(Qt.DateFormat f)
          Returns a string representation of the com.trolltech.qt.core.Qt$DateFormat argument.
 java.lang.String toString(java.lang.String format)
          Returns a string representation of the java.lang.String argument.
 int toTime_t()
          Returns the datetime as the number of seconds that have passed since 1970-01-01T00.00:00, Coordinated Universal Time (Qt::UTC ).
 QDateTime toTimeSpec(Qt.TimeSpec spec)
          Returns a copy of this datetime configured to use the given time specification.
 QDateTime toUTC()
          Returns a datetime containing the date and time information in this datetime, but specified using the Qt::UTC definition.
 void writeTo(QDataStream arg__1)
          Writes thisQDateTime
 
Methods inherited from class com.trolltech.qt.QtJambiObject
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr
 
Methods inherited from class com.trolltech.qt.QSignalEmitter
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread
 
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
__qt_signalInitialization
 
Methods inherited from class java.lang.Object
getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.lang.Comparable
compareTo
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

QDateTime

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

See also:
isValid().


QDateTime

public QDateTime(QDate arg__1)
Constructs a datetime with the given date, a valid time(00.00:00. 00), and sets the timeSpec() to Qt::LocalTime .


QDateTime

public QDateTime(QDate arg__1,
                 QTime arg__2)
Constructs a datetime with the given date and time, using the time specification defined by spec.

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


QDateTime

public QDateTime(QDate arg__1,
                 QTime arg__2,
                 Qt.TimeSpec spec)
Constructs a datetime with the given date and time, using the time specification defined by spec.

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


QDateTime

public QDateTime(QDateTime other)
Constructs a copy of the other datetime.

Method Detail

addDays

public final QDateTime addDays(int days)
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().


addMSecs

public final QDateTime addMSecs(long msecs)
Returns a QDateTime object containing a datetime msecs miliseconds later than the datetime of this object (or earlier if msecs is negative).

See also:
addSecs(), secsTo(), addDays(), addMonths(), and addYears().


addMonths

public final QDateTime addMonths(int months)
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().


addSecs

public final QDateTime addSecs(int secs)
Returns a QDateTime object containing a datetime s seconds later than the datetime of this object (or earlier if s is negative).

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


addYears

public final QDateTime addYears(int years)
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().


date

public final QDate date()
Returns the date part of the datetime.

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


daysTo

public final int daysTo(QDateTime arg__1)
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().


isNull

public final boolean isNull()
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().


isValid

public final boolean isValid()
Returns true if both the date and the time are valid; otherwise returns false.

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


writeTo

public final void writeTo(QDataStream arg__1)
Writes thisQDateTime


readFrom

public final void readFrom(QDataStream arg__1)
Reads a QDateTime


secsTo

public final int secsTo(QDateTime arg__1)
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 one of the two datetimes has daylight saving time (DST) and the other doesn't.

Example:

        QDateTime now = QDateTime.currentDateTime();
        QDateTime xmas = new QDateTime(new QDate(now.date().year(), 12, 25), new QTime(0, 0));
        System.err.println("There are " + now.secsTo(xmas) + "seconds to Christmas");

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


setDate

public final void setDate(QDate date)
Sets the date part of this datetime to date. If no time is set, it is set to midnight.

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


setTime

public final void setTime(QTime time)
Sets the time part of this datetime to time.

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


setTimeSpec

public final void setTimeSpec(Qt.TimeSpec spec)
Sets the time specification used in this datetime to spec.

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


setTime_t

public final void setTime_t(int secsSince1Jan1970UTC)
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 time zones this function will behave as if local time were Qt::UTC .

See also:
toTime_t().


time

public final QTime time()
Returns the time part of the datetime.

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


timeSpec

public final Qt.TimeSpec timeSpec()
Returns the time specification of the datetime.

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


toLocalTime

public final QDateTime toLocalTime()
Returns a datetime containing the date and time information in this datetime, but specified using the Qt::LocalTime definition.

See also:
toTimeSpec().


toString

public final java.lang.String toString()
Returns a string representation of the this QDateTime.

Overrides:
toString in class java.lang.Object

toString

public final java.lang.String toString(Qt.DateFormat f)
Returns a string representation of the com.trolltech.qt.core.Qt$DateFormat argument.


toString

public final java.lang.String toString(java.lang.String format)
Returns a string representation of the java.lang.String argument.


toTimeSpec

public final QDateTime toTimeSpec(Qt.TimeSpec spec)
Returns a copy of this datetime configured to use the given time specification.

See also:
timeSpec(), toUTC(), and toLocalTime().


toTime_t

public final int toTime_t()
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 time zones, this function will behave as if local time were Qt::UTC .

See also:
setTime_t().


toUTC

public final QDateTime toUTC()
Returns a datetime containing the date and time information in this datetime, but specified using the Qt::UTC definition.

See also:
toTimeSpec().


currentDateTime

public static QDateTime currentDateTime()
Returns the current datetime, as reported by the system clock, in the local time zone.

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


fromString

public static QDateTime fromString(java.lang.String s)
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.


fromString

public static QDateTime fromString(java.lang.String s,
                                   Qt.DateFormat f)
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.


fromString

public static QDateTime fromString(java.lang.String s,
                                   java.lang.String format)
Returns the QDateTime represented by the string, using the format given, or an invalid datetime if the string cannot be parsed.

These expressions may be used for the date part of the format string:

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. 'Monday' to '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
Note: Unlike the other version of this function, day and month names must be given in the user's local language. It is only possible to use the English names if the user's language is English.

These expressions may be used for the time part of the format string:

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 interpret as an AM/PM time. AP must be either "AM" or "PM".
ap or a 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 singlequotes will also be treated as text and not be used as an expression.
        QTime time1 = QTime.fromString("131", "HHh");
        // time1 is 13:00:00
        QTime time2 = 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. 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 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.

For any field that is not represented in the format the following defaults are used:

Field
Default value
Year 1900
Month 1 (January)
Day 1
Hour 0
Minute 0
Second 0
For example:
        QDateTime dateTime = QDateTime.fromString("1.30.1", "M.d.s");
        // dateTime is January 30 in the current year 00:00:01
QDateTime::toString()QTime::toString()

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


fromTime_t

public static QDateTime fromTime_t(int secsSince1Jan1970UTC)
Returns a datetime whose date and time are the number of seconds that have passed since 1970-01-01T00.00:00, Coordinated Universal Time (Qt::UTC ). On systems that do not support time zones, the time will be set as if local time were Qt::UTC .

See also:
toTime_t(), and setTime_t().


clone

public QDateTime clone()
This method is reimplemented for internal reasons

Overrides:
clone in class java.lang.Object