Converts between UTC and local time in a specific time zone. More...

Classes
class	OffsetData
	Time Zone offset data for a given time More...

Public Typedefs
typedef QVector< OffsetData >	OffsetDataList

Public Types
enum	NameType

enum	TimeType

Public Methods
	QTimeZone (const QByteArray &zoneId)

	QTimeZone (const QByteArray &zoneId, int offsetSeconds, const QString &name, const QString &abbreviation, QLocale::Country country=QLocale::AnyCountry, const QString &comment=QString ())

	QTimeZone (const QTimeZone &other)

	QTimeZone (int offsetSeconds)

	~QTimeZone ()

QString	abbreviation (const QDateTime &atDateTime) const

QString	comment () const

QLocale::Country	country () const

int	daylightTimeOffset (const QDateTime &atDateTime) const

QString	displayName (const QDateTime &atDateTime, QTimeZone::NameType nameType=QTimeZone::DefaultName, const QLocale &locale=QLocale ()) const

QString	displayName (QTimeZone::TimeType timeType, QTimeZone::NameType nameType=QTimeZone::DefaultName, const QLocale &locale=QLocale ()) const

bool	hasDaylightTime () const

bool	hasTransitions () const

QByteArray	id () const

bool	isDaylightTime (const QDateTime &atDateTime) const

bool	isValid () const

OffsetData	nextTransition (const QDateTime &afterDateTime) const

OffsetData	offsetData (const QDateTime &forDateTime) const

int	offsetFromUtc (const QDateTime &atDateTime) const

bool	operator!= (const QTimeZone &other) const

QTimeZone &	operator= (const QTimeZone &other)

QTimeZone &	operator= (QTimeZone &&other)

bool	operator== (const QTimeZone &other) const

OffsetData	previousTransition (const QDateTime &beforeDateTime) const

int	standardTimeOffset (const QDateTime &atDateTime) const

void	swap (QTimeZone &other)

OffsetDataList	transitions (const QDateTime &fromDateTime, const QDateTime &toDateTime) const

Static Public Methods
static QList< QByteArray >	availableTimeZoneIds ()

static QList< QByteArray >	availableTimeZoneIds (int offsetSeconds)

static QList< QByteArray >	availableTimeZoneIds (QLocale::Country country)

static QByteArray	ianaIdToWindowsId (const QByteArray &zoneId)

static bool	isTimeZoneIdAvailable (const QByteArray &zoneId)

static QTimeZone	systemTimeZone ()

static QByteArray	systemTimeZoneId ()

static QTimeZone	utc ()

static QByteArray	windowsIdToDefaultIanaId (const QByteArray &windowsId)

static QByteArray	windowsIdToDefaultIanaId (const QByteArray &windowsId, QLocale::Country country)

static QList< QByteArray >	windowsIdToIanaIds (const QByteArray &windowsId)

static QList< QByteArray >	windowsIdToIanaIds (const QByteArray &windowsId, QLocale::Country country)

Friends
QDataStream &	operator<< (QDataStream &stream, const QTimeZone &tz)

class	QDateTime

Related Functions
These are not member functions
QDataStream &	operator>> (QDataStream &stream, QTimeZone &tz)

Detailed Description

This class provides a stateless calculator for time zone conversions between UTC and the local time in a specific time zone. By default it uses the host system time zone data to perform these conversions.

This class is primarily designed for use in QDateTime; most applications will not need to access this class directly and should instead use QDateTime with a Qt::TimeSpec of Qt::TimeZone.

Note: For consistency with QDateTime, QTimeZone does not account for leap seconds.

IANA Time Zone IDs

QTimeZone uses the IANA time zone IDs as defined in the IANA Time Zone Database (http://www.iana.org/time-zones). This is to ensure a standard ID across all supported platforms. Most platforms support the IANA IDs and the IANA Database natively, but for Windows a mapping is required to the native IDs.

The IANA IDs can and do change on a regular basis, and can vary depending on how recently the host system data was updated. As such you cannot rely on any given ID existing on any host system. You must use availableTimeZoneIds() to determine what IANA IDs are available.

The IANA IDs and database are also know as the Olson IDs and database, named after their creator.

UTC Offset Time Zones

A default UTC time zone backend is provided which is always guaranteed to be available. This provides a set of generic Offset From UTC time zones in the range UTC-14:00 to UTC+14:00. These time zones can be created using either the standard ISO format names "UTC+00:00" as listed by availableTimeZoneIds(), or using the number of offset seconds.

Windows Time Zones

Windows native time zone support is severely limited compared to the standard IANA TZ Database. Windows time zones cover larger geographic areas and are thus less accurate in their conversions. They also do not support as much historic conversion data and so may only be accurate for the current year.

QTimeZone uses a conversion table derived form the Unicode CLDR data to map between IANA IDs and Windows IDs. Depending on your version of Windows this table may not be able to provide a valid conversion, in which "UTC" will be returned.

QTimeZone provides a public API to use this conversion table. The Windows ID used is the Windows Registry Key for the time zone which is also the MS Exchange EWS ID as well, but is different to the Time Zone Name (TZID) and COD code used by MS Exchange in versions before 2007.

System Time Zone

QTimeZone does not support any concept of a system or default time zone. If you require a QDateTime that uses the current system time zone at any given moment then you should use a Qt::TimeSpec of Qt::LocalTime.

The method systemTimeZoneId() returns the current system IANA time zone ID which on Unix-like systems will always be correct. On Windows this ID is translated from the Windows system ID using an internal translation table and the user's selected country. As a consequence there is a small chance any Windows install may have IDs not known by QTimeZone, in which case "UTC" will be returned.

Creating a new QTimeZone instance using the system time zone ID will only produce a fixed named copy of the time zone, it will not change if the system time zone changes.

Time Zone Offsets

The difference between UTC and the local time in a time zone is expressed as an offset in seconds from UTC, i.e. the number of seconds to add to UTC to obtain the local time. The total offset is comprised of two component parts, the standard time offset and the daylight-saving time offset. The standard time offset is the number of seconds to add to UTC to obtain standard time in the time zone. The daylight-saving time offset is the number of seconds to add to the standard time offset to obtain daylight-saving time (abbreviated DST and sometimes called "daylight time" or "summer time") in the time zone.

Note that the standard and DST offsets for a time zone may change over time as countries have changed DST laws or even their standard time offset.

License

This class includes data obtained from the CLDR data files under the terms of the Unicode license.

See also: QDateTime

Member Typedef Documentation

QTimeZone::OffsetDataList

Synonym for QVector<OffsetData>.

Member Enumeration Documentation

enum QTimeZone::NameType

The type of time zone name.

Constant	Value	Description
QTimeZone::DefaultName	0	The default form of the time zone name, e.g. LongName, ShortName or OffsetName
QTimeZone::LongName	1	The long form of the time zone name, e.g. "Central European Time"
QTimeZone::ShortName	2	The short form of the time zone name, usually an abbreviation, e.g. "CET"
QTimeZone::OffsetName	3	The standard ISO offset form of the time zone name, e.g. "UTC+01:00"e

enum QTimeZone::TimeType

The type of time zone time, for example when requesting the name. In time zones that do not apply DST, all three values may return the same result.

Constant	Value	Description
QTimeZone::StandardTime	0	The standard time in a time zone, i.e. when Daylight-Saving is not in effect. For example when formatting a display name this will show something like "Pacific Standard Time".
QTimeZone::DaylightTime	1	A time when Daylight-Saving is in effect. For example when formatting a display name this will show something like "Pacific daylight-saving time".
QTimeZone::GenericTime	2	A time which is not specifically Standard or Daylight-Saving time, either an unknown time or a neutral form. For example when formatting a display name this will show something like "Pacific Time".

Constructor & Destructor Documentation

QTimeZone::QTimeZone ( const QByteArray & zoneId )

explicit

Creates an instance of the requested time zone zoneId. The ID must be one of the available system IDs otherwise an invalid time zone will be returned.

See also: availableTimeZoneIds()

QTimeZone::QTimeZone ( int offsetSeconds )

explicit

Creates an instance of a time zone with the requested Offset from UTC of offsetSeconds.

The offsetSeconds from UTC must be in the range -14 hours to +14 hours otherwise an invalid time zone will be returned.

QTimeZone::QTimeZone	(	const QByteArray &	zoneId,
		int	offsetSeconds,
		const QString &	name,
		const QString &	abbreviation,
		QLocale::Country	country = `QLocale::AnyCountry`,
		const QString &	comment = `QString()`
	)

Creates a custom time zone with an ID of zoneId and an offset from UTC of offsetSeconds. The name will be the name used by displayName() for the LongName, the abbreviation will be used by displayName() for the ShortName and by abbreviation(), and the optional country will be used by country(). The comment is an optional note that may be displayed in a GUI to assist users in selecting a time zone.

The zoneId must not be one of the available system IDs returned by availableTimeZoneIds(). The offsetSeconds from UTC must be in the range -14 hours to +14 hours.

If the custom time zone does not have a specific country then set it to the default value of QLocale::AnyCountry.

QTimeZone::QTimeZone ( const QTimeZone & other )

Copy constructs a new QTimeZone from other.

QTimeZone::~QTimeZone ( )

Destroys the time zone.

Method Documentation

QString QTimeZone::abbreviation ( const QDateTime & atDateTime ) const

Returns the time zone abbreviation at the given atDateTime. The abbreviation may change depending on DST or even historical events.

Note that the abbreviation is not guaranteed to be unique to this time zone and should not be used in place of the ID or display name.

See also: displayName()

QList< QByteArray > QTimeZone::availableTimeZoneIds ( )

static

Returns a list of all available IANA time zone IDs on this system.

See also: isTimeZoneIdAvailable()

QList< QByteArray > QTimeZone::availableTimeZoneIds ( int offsetSeconds )

static

Returns a list of all available IANA time zone IDs with a given standard time offset of offsetSeconds.

See also: isTimeZoneIdAvailable()

QList< QByteArray > QTimeZone::availableTimeZoneIds ( QLocale::Country country )

static

Returns a list of all available IANA time zone IDs for a given country.

As a special case, a country of Qt::AnyCountry returns those time zones that do not have any country related to them, such as UTC. If you require a list of all time zone IDs for all countries then use the standard availableTimeZoneIds() method.

See also: isTimeZoneIdAvailable()

QString QTimeZone::comment ( ) const

Returns any comment for the time zone. A comment may be provided by the host platform to assist users in choosing the correct time zone. Depending on the platform this may not be localized.

QLocale::Country QTimeZone::country ( ) const

Returns the country for the time zone.

int QTimeZone::daylightTimeOffset ( const QDateTime & atDateTime ) const

Returns the daylight-saving time offset at the given atDateTime, i.e. the number of seconds to add to the standard time offset to obtain the local daylight-saving time.

For example, for the time zone "Europe/Berlin" the DST offset is +3600 seconds. During standard time daylightTimeOffset() will return 0, and when daylight-saving is in effect it will return +3600.

See also: offsetFromUtc(), standardTimeOffset()

QString QTimeZone::displayName	(	const QDateTime &	atDateTime,
		QTimeZone::NameType	nameType = `QTimeZone::DefaultName`,
		const QLocale &	locale = `QLocale()`
	)		const

Returns the localized time zone display name at the given atDateTime for the given nameType in the given locale. The nameType and locale requested may not be supported on all platforms, in which case the best available option will be returned.

If the locale is not provided then the application default locale will be used.

The display name may change depending on DST or historical events.

See also: abbreviation()

QString QTimeZone::displayName	(	QTimeZone::TimeType	timeType,
		QTimeZone::NameType	nameType = `QTimeZone::DefaultName`,
		const QLocale &	locale = `QLocale()`
	)		const

Returns the localized time zone display name for the given timeType and nameType in the given locale. The nameType and locale requested may not be supported on all platforms, in which case the best available option will be returned.

If the locale is not provided then the application default locale will be used.

Where the time zone display names have changed over time then the most recent names will be used.

See also: abbreviation()

bool QTimeZone::hasDaylightTime ( ) const

Returns true if the time zone has practiced daylight-saving at any time.

See also: isDaylightTime(), daylightTimeOffset()

bool QTimeZone::hasTransitions ( ) const

Returns true if the system backend supports obtaining transitions.

Transitions are changes in the time-zone: these happen when DST turns on or off and when authorities alter the offsets for the time-zone.

See also: nextTransition(), previousTransition(), transitions()

QByteArray QTimeZone::ianaIdToWindowsId ( const QByteArray & zoneId )

static

Returns the Windows ID equivalent to the given zoneId.

See also: windowsIdToDefaultIanaId(), windowsIdToIanaIds()

QByteArray QTimeZone::id ( ) const

Returns the IANA ID for the time zone.

IANA IDs are used on all platforms. On Windows these are translated from the Windows ID into the closest IANA ID for the time zone and country.

bool QTimeZone::isDaylightTime ( const QDateTime & atDateTime ) const

Returns true if daylight-saving was in effect at the given atDateTime.

See also: hasDaylightTime(), daylightTimeOffset()

bool QTimeZone::isTimeZoneIdAvailable ( const QByteArray & zoneId )

static

Returns true if a given time zone zoneId is available on this system.

See also: availableTimeZoneIds()

bool QTimeZone::isValid ( ) const

Returns true if this time zone is valid.

QTimeZone::OffsetData QTimeZone::nextTransition ( const QDateTime & afterDateTime ) const

Returns the first time zone Transition after the given afterDateTime. This is useful when you have a Transition time and want to find the Transition after it.

If there is no transition after the given afterDateTime then an invalid OffsetData will be returned with an invalid QDateTime.

See also: hasTransitions(), previousTransition(), transitions()

QTimeZone::OffsetData QTimeZone::offsetData ( const QDateTime & forDateTime ) const

Returns the effective offset details at the given forDateTime. This is equivalent to calling offsetFromUtc(), abbreviation(), etc individually but is more efficient.

See also: offsetFromUtc(), standardTimeOffset(), daylightTimeOffset(), abbreviation()

int QTimeZone::offsetFromUtc ( const QDateTime & atDateTime ) const

Returns the total effective offset at the given atDateTime, i.e. the number of seconds to add to UTC to obtain the local time. This includes any DST offset that may be in effect, i.e. it is the sum of standardTimeOffset() and daylightTimeOffset() for the given datetime.

For example, for the time zone "Europe/Berlin" the standard time offset is +3600 seconds and the DST offset is +3600 seconds. During standard time offsetFromUtc() will return +3600 (UTC+01:00), and during DST it will return +7200 (UTC+02:00).

See also: standardTimeOffset(), daylightTimeOffset()

bool QTimeZone::operator!= ( const QTimeZone & other ) const

Returns true if this time zone is not equal to the other time zone.

QTimeZone & QTimeZone::operator= ( const QTimeZone & other )

Assignment operator, assign other to this.

QTimeZone & QTimeZone::operator= ( QTimeZone && other )

inline

Move assigns other to this QTimeZone instance, transferring the ownership of the managed pointer to this instance.

bool QTimeZone::operator== ( const QTimeZone & other ) const

Returns true if this time zone is equal to the other time zone.

QTimeZone::OffsetData QTimeZone::previousTransition ( const QDateTime & beforeDateTime ) const

Returns the first time zone Transition before the given beforeDateTime. This is useful when you have a Transition time and wish to find the Transition before it.

If there is no transition before the given beforeDateTime then an invalid OffsetData will be returned with an invalid QDateTime.

See also: hasTransitions(), nextTransition(), transitions()

int QTimeZone::standardTimeOffset ( const QDateTime & atDateTime ) const

Returns the standard time offset at the given atDateTime, i.e. the number of seconds to add to UTC to obtain the local Standard Time. This excludes any DST offset that may be in effect.

For example, for the time zone "Europe/Berlin" the standard time offset is +3600 seconds. During both standard and DST offsetFromUtc() will return +3600 (UTC+01:00).

See also: offsetFromUtc(), daylightTimeOffset()

void QTimeZone::swap ( QTimeZone & other )

inline

Swaps this time zone instance with other. This function is very fast and never fails.

QTimeZone QTimeZone::systemTimeZone ( )

static

Returns a QTimeZone object that refers to the local system time, as specified by systemTimeZoneId().

See also: utc()

QByteArray QTimeZone::systemTimeZoneId ( )

static

Returns the current system time zone IANA ID.

On Windows this ID is translated from the Windows ID using an internal translation table and the user's selected country. As a consequence there is a small chance any Windows install may have IDs not known QTimeZone in which case "UTC" will be returned.

QTimeZone::OffsetDataList QTimeZone::transitions	(	const QDateTime &	fromDateTime,
		const QDateTime &	toDateTime
	)		const

Returns a list of all time zone transitions between the given datetimes. The given fromDateTime and toDateTime are inclusive.

See also: hasTransitions(), nextTransition(), previousTransition()

QTimeZone QTimeZone::utc ( )

static

Returns a QTimeZone object that refers to UTC (Universal Time Coordinated).

See also: systemTimeZone()

QByteArray QTimeZone::windowsIdToDefaultIanaId ( const QByteArray & windowsId )

static

Returns the default IANA ID for a given windowsId.

Because a Windows ID can cover several IANA IDs in several different countries, this function returns the most frequently used IANA ID with no regard for the country and should thus be used with care. It is usually best to request the default for a specific country.

See also: ianaIdToWindowsId(), windowsIdToIanaIds()

QByteArray QTimeZone::windowsIdToDefaultIanaId	(	const QByteArray &	windowsId,
		QLocale::Country	country
	)

static

Returns the default IANA ID for a given windowsId and country.

Because a Windows ID can cover several IANA IDs within a given country, the most frequently used IANA ID in that country is returned.

As a special case, QLocale::AnyCountry returns the default of those IANA IDs that do not have any specific country.

See also: ianaIdToWindowsId(), windowsIdToIanaIds()

QList< QByteArray > QTimeZone::windowsIdToIanaIds ( const QByteArray & windowsId )

static

Returns all the IANA IDs for a given windowsId. The returned list is sorted alphabetically.

See also: ianaIdToWindowsId(), windowsIdToDefaultIanaId()

QList< QByteArray > QTimeZone::windowsIdToIanaIds	(	const QByteArray &	windowsId,
		QLocale::Country	country
	)

static

Returns all the IANA IDs for a given windowsId and country.

As a special case QLocale::AnyCountry returns those IANA IDs that do not have any specific country. The returned list is in order of frequency of usage, i.e. larger zones within a country are listed first.

See also: ianaIdToWindowsId(), windowsIdToDefaultIanaId()

Friends And Related Function Documentation

QDataStream & operator<<	(	QDataStream &	stream,
		const QTimeZone &	tz
	)

friend

Writes the given tz to the stream. Returns a reference to the stream.

Refer to Serializing Data Types for additional information.

QDataStream & operator>>	(	QDataStream &	stream,
		QTimeZone &	tz
	)

Refer to Serializing Data Types for additional information.

Classes

Public Typedefs

Public Types

Public Methods

Static Public Methods

Friends

Related Functions

Detailed Description

IANA Time Zone IDs

UTC Offset Time Zones

Windows Time Zones

System Time Zone

Time Zone Offsets

License

Member Typedef Documentation

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation

Friends And Related Function Documentation