TimeZone represents a time zone offset, and also figures out daylight savings. More...

#include <timezone.h>

Inheritance diagram for icu::TimeZone:

Public Types
enum	EDisplayType { SHORT = 1, LONG, SHORT_GENERIC, LONG_GENERIC, SHORT_GMT, LONG_GMT, SHORT_COMMONLY_USED, GENERIC_LOCATION }
	Enum for use with getDisplayName. More...

Public Member Functions
virtual	~TimeZone ()

virtual UBool	operator== (const TimeZone &that) const
	Returns true if the two TimeZones are equal. More...

UBool	operator!= (const TimeZone &that) const
	Returns true if the two TimeZones are NOT equal; that is, if operator==() returns false. More...

virtual int32_t	getOffset (uint8_t era, int32_t year, int32_t month, int32_t day, uint8_t dayOfWeek, int32_t millis, UErrorCode &status) const =0
	Returns the TimeZone's adjusted GMT offset (i.e., the number of milliseconds to add to GMT to get local time in this time zone, taking daylight savings time into account) as of a particular reference date. More...

virtual int32_t	getOffset (uint8_t era, int32_t year, int32_t month, int32_t day, uint8_t dayOfWeek, int32_t milliseconds, int32_t monthLength, UErrorCode &status) const =0
	Gets the time zone offset, for current date, modified in case of daylight savings. More...

virtual void	getOffset (UDate date, UBool local, int32_t &rawOffset, int32_t &dstOffset, UErrorCode &ec) const
	Returns the time zone raw and GMT offset for the given moment in time. More...

virtual void	setRawOffset (int32_t offsetMillis)=0
	Sets the TimeZone's raw GMT offset (i.e., the number of milliseconds to add to GMT to get local time, before taking daylight savings time into account). More...

virtual int32_t	getRawOffset (void) const =0
	Returns the TimeZone's raw GMT offset (i.e., the number of milliseconds to add to GMT to get local time, before taking daylight savings time into account). More...

UnicodeString &	getID (UnicodeString &ID) const
	Fills in "ID" with the TimeZone's ID. More...

void	setID (const UnicodeString &ID)
	Sets the TimeZone's ID to the specified value. More...

UnicodeString &	getDisplayName (UnicodeString &result) const
	Returns a name of this time zone suitable for presentation to the user in the default locale. More...

UnicodeString &	getDisplayName (const Locale &locale, UnicodeString &result) const
	Returns a name of this time zone suitable for presentation to the user in the specified locale. More...

UnicodeString &	getDisplayName (UBool inDaylight, EDisplayType style, UnicodeString &result) const
	Returns a name of this time zone suitable for presentation to the user in the default locale. More...

UnicodeString &	getDisplayName (UBool inDaylight, EDisplayType style, const Locale &locale, UnicodeString &result) const
	Returns a name of this time zone suitable for presentation to the user in the specified locale. More...

virtual UBool	useDaylightTime (void) const =0
	Queries if this time zone uses daylight savings time. More...

virtual UBool	inDaylightTime (UDate date, UErrorCode &status) const =0
	Queries if the given date is in daylight savings time in this time zone. More...

virtual UBool	hasSameRules (const TimeZone &other) const
	Returns true if this zone has the same rule and offset as another zone. More...

virtual TimeZone *	clone (void) const =0
	Clones TimeZone objects polymorphically. More...

virtual UClassID	getDynamicClassID (void) const =0
	Returns a unique class ID POLYMORPHICALLY. More...

virtual int32_t	getDSTSavings () const
	Returns the amount of time to be added to local standard time to get local wall clock time. More...

Public Member Functions inherited from icu::UObject
virtual	~UObject ()
	Destructor. More...

Static Public Member Functions
static const TimeZone &	getUnknown ()
	Returns the "unknown" time zone. More...

static const TimeZone *	getGMT (void)
	The GMT (=UTC) time zone has a raw offset of zero and does not use daylight savings time. More...

static TimeZone *	createTimeZone (const UnicodeString &ID)
	Creates a `TimeZone` for the given ID. More...

static StringEnumeration *	createTimeZoneIDEnumeration (USystemTimeZoneType zoneType, const char region, const int32_t rawOffset, UErrorCode &ec)
	Returns an enumeration over system time zone IDs with the given filter conditions. More...

static StringEnumeration *	createEnumeration ()
	Returns an enumeration over all recognized time zone IDs. More...

static StringEnumeration *	createEnumeration (int32_t rawOffset)
	Returns an enumeration over time zone IDs with a given raw offset from GMT. More...

static StringEnumeration *	createEnumeration (const char *country)
	Returns an enumeration over time zone IDs associated with the given country. More...

static int32_t	countEquivalentIDs (const UnicodeString &id)
	Returns the number of IDs in the equivalency group that includes the given ID. More...

static const UnicodeString	getEquivalentID (const UnicodeString &id, int32_t index)
	Returns an ID in the equivalency group that includes the given ID. More...

static TimeZone *	detectHostTimeZone ()
	Creates an instance of TimeZone detected from the current host system configuration. More...

static TimeZone *	createDefault (void)
	Creates a new copy of the default TimeZone for this host. More...

static void	adoptDefault (TimeZone *zone)
	Sets the default time zone (i.e., what's returned by createDefault()) to be the specified time zone. More...

static void	setDefault (const TimeZone &zone)
	Same as adoptDefault(), except that the TimeZone object passed in is NOT adopted; the caller remains responsible for deleting it. More...

static const char *	getTZDataVersion (UErrorCode &status)
	Returns the timezone data version currently used by ICU. More...

static UnicodeString &	getCanonicalID (const UnicodeString &id, UnicodeString &canonicalID, UErrorCode &status)
	Returns the canonical system timezone ID or the normalized custom time zone ID for the given time zone ID. More...

static UnicodeString &	getCanonicalID (const UnicodeString &id, UnicodeString &canonicalID, UBool &isSystemID, UErrorCode &status)
	Returns the canonical system time zone ID or the normalized custom time zone ID for the given time zone ID. More...

static UnicodeString &	getWindowsID (const UnicodeString &id, UnicodeString &winid, UErrorCode &status)
	Converts a system time zone ID to an equivalent Windows time zone ID. More...

static UnicodeString &	getIDForWindowsID (const UnicodeString &winid, const char *region, UnicodeString &id, UErrorCode &status)
	Converts a Windows time zone ID to an equivalent system time zone ID for a region. More...

static UClassID	getStaticClassID (void)
	Return the class ID for this class. More...

static int32_t	getRegion (const UnicodeString &id, char *region, int32_t capacity, UErrorCode &status)
	Gets the region code associated with the given system time zone ID. More...

static const char16_t *	getRegion (const UnicodeString &id, UErrorCode &status)
	Returns the region code associated with the given zone, or NULL if the zone is not known. More...

Protected Member Functions
	TimeZone ()
	Default constructor. More...

	TimeZone (const UnicodeString &id)
	Construct a TimeZone with a given ID. More...

	TimeZone (const TimeZone &source)
	Copy constructor. More...

TimeZone &	operator= (const TimeZone &right)
	Default assignment operator. More...

Static Protected Member Functions
static UResourceBundle *	loadRule (const UResourceBundle top, const UnicodeString &ruleid, UResourceBundle oldbundle, UErrorCode &status)
	Utility function. More...

Friends
class	ZoneMeta

class	TZEnumeration

Detailed Description

TimeZone represents a time zone offset, and also figures out daylight savings.

Typically, you get a TimeZone using createDefault which creates a TimeZone based on the time zone where the program is running. For example, for a program running in Japan, createDefault creates a TimeZone object based on Japanese Standard Time.

You can also get a TimeZone using createTimeZone along with a time zone ID. For instance, the time zone ID for the US Pacific Time zone is "America/Los_Angeles". So, you can get a Pacific Time TimeZone object with:

TimeZone *tz = TimeZone::createTimeZone("America/Los_Angeles");

You can use the createEnumeration method to iterate through all the supported time zone IDs, or the getCanonicalID method to check if a time zone ID is supported or not. You can then choose a supported ID to get a TimeZone. If the time zone you want is not represented by one of the supported IDs, then you can create a custom time zone ID with the following syntax:

GMT[+|-]hh[[:]mm]

For example, you might specify GMT+14:00 as a custom time zone ID. The TimeZone that is returned when you specify a custom time zone ID uses the specified offset from GMT(=UTC) and does not observe daylight saving time. For example, you might specify GMT+14:00 as a custom time zone ID to create a TimeZone representing 14 hours ahead of GMT (with no daylight saving time). In addition, getCanonicalID can also be used to normalize a custom time zone ID.

TimeZone is an abstract class representing a time zone. A TimeZone is needed for Calendar to produce local time for a particular time zone. A TimeZone comprises three basic pieces of information:

A time zone offset; that, is the number of milliseconds to add or subtract from a time expressed in terms of GMT to convert it to the same time in that time zone (without taking daylight savings time into account).
Logic necessary to take daylight savings time into account if daylight savings time is observed in that time zone (e.g., the days and hours on which daylight savings time begins and ends).
An ID. This is a text string that uniquely identifies the time zone.

(Only the ID is actually implemented in TimeZone; subclasses of TimeZone may handle daylight savings time and GMT offset in different ways. Currently we have the following TimeZone subclasses: RuleBasedTimeZone, SimpleTimeZone, and VTimeZone.)

The TimeZone class contains a static list containing a TimeZone object for every combination of GMT offset and daylight-savings time rules currently in use in the world, each with a unique ID. Each ID consists of a region (usually a continent or ocean) and a city in that region, separated by a slash, (for example, US Pacific Time is "America/Los_Angeles.") Because older versions of this class used three- or four-letter abbreviations instead, there is also a table that maps the older abbreviations to the newer ones (for example, "PST" maps to "America/Los_Angeles"). Anywhere the API requires an ID, you can use either form.

To create a new TimeZone, you call the factory function TimeZone::createTimeZone() and pass it a time zone ID. You can use the createEnumeration() function to obtain a list of all the time zone IDs recognized by createTimeZone().

You can also use TimeZone::createDefault() to create a TimeZone. This function uses platform-specific APIs to produce a TimeZone for the time zone corresponding to the client's computer's physical location. For example, if you're in Japan (assuming your machine is set up correctly), TimeZone::createDefault() will return a TimeZone for Japanese Standard Time ("Asia/Tokyo").

Definition at line 131 of file timezone.h.

Member Enumeration Documentation

◆ EDisplayType

enum icu::TimeZone::EDisplayType

Enum for use with getDisplayName.

Stable:: ICU 2.4

Enumerator
SHORT	Selector for short display name. Stable: ICU 2.4
LONG	Selector for long display name. Stable: ICU 2.4
SHORT_GENERIC	Selector for short generic display name. Stable: ICU 4.4
LONG_GENERIC	Selector for long generic display name. Stable: ICU 4.4
SHORT_GMT	Selector for short display name derived from time zone offset. Stable: ICU 4.4
LONG_GMT	Selector for long display name derived from time zone offset. Stable: ICU 4.4
SHORT_COMMONLY_USED	Selector for short display name derived from the time zone's fallback name. Stable: ICU 4.4
GENERIC_LOCATION	Selector for long display name derived from the time zone's fallback name. Stable: ICU 4.4

Definition at line 588 of file timezone.h.

Constructor & Destructor Documentation

◆ ~TimeZone()

virtual icu::TimeZone::~TimeZone ( )

virtual

Stable:: ICU 2.0

◆ TimeZone() [1/3]

icu::TimeZone::TimeZone ( )

protected

Default constructor.

ID is initialized to the empty string.

Stable:: ICU 2.0

◆ TimeZone() [2/3]

icu::TimeZone::TimeZone ( const UnicodeString & id )

protected

Construct a TimeZone with a given ID.

Parameters

id	a system time zone ID

Stable:: ICU 2.0

◆ TimeZone() [3/3]

icu::TimeZone::TimeZone ( const TimeZone & source )

protected

Copy constructor.

Parameters

source the object to be copied.

Stable:: ICU 2.0

Member Function Documentation

◆ adoptDefault()

static void icu::TimeZone::adoptDefault ( TimeZone * zone )

static

Sets the default time zone (i.e., what's returned by createDefault()) to be the specified time zone.

If NULL is specified for the time zone, the default time zone is set to the default host time zone. This call adopts the TimeZone object passed in; the client is no longer responsible for deleting it.

This function is not thread safe. It is an error for multiple threads to concurrently attempt to set the default time zone, or for any thread to attempt to reference the default zone while another thread is setting it.

Parameters

zone	A pointer to the new TimeZone object to use as the default.

Stable:: ICU 2.0

◆ clone()

virtual TimeZone* icu::TimeZone::clone ( void ) const

pure virtual

Clones TimeZone objects polymorphically.

Clients are responsible for deleting the TimeZone object cloned.

Returns: A new copy of this TimeZone object.

Stable:: ICU 2.0

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ countEquivalentIDs()

static int32_t icu::TimeZone::countEquivalentIDs ( const UnicodeString & id )

static

Returns the number of IDs in the equivalency group that includes the given ID.

An equivalency group contains zones that have the same GMT offset and rules.

The returned count includes the given ID; it is always >= 1. The given ID must be a system time zone. If it is not, returns zero.

Parameters

id	a system time zone ID

Returns: the number of zones in the equivalency group containing 'id', or zero if 'id' is not a valid system ID

See also: getEquivalentID

Stable:: ICU 2.0

◆ createDefault()

static TimeZone* icu::TimeZone::createDefault ( void )

static

Creates a new copy of the default TimeZone for this host.

Unless the default time zone has already been set using adoptDefault() or setDefault(), the default is determined by querying the host system configuration. If the host system detection routines fail, or if they specify a TimeZone or TimeZone offset which is not recognized, then the special TimeZone "Etc/Unknown" is instantiated and made the default.

Returns: A default TimeZone. Clients are responsible for deleting the time zone object returned.

See also: getUnknown

Stable:: ICU 2.0

◆ createEnumeration() [1/3]

static StringEnumeration* icu::TimeZone::createEnumeration ( )

static

Returns an enumeration over all recognized time zone IDs.

(i.e., all strings that createTimeZone() accepts)

Returns: an enumeration object, owned by the caller.

Stable:: ICU 2.4

◆ createEnumeration() [2/3]

static StringEnumeration* icu::TimeZone::createEnumeration ( int32_t rawOffset )

static

Returns an enumeration over time zone IDs with a given raw offset from GMT.

There may be several times zones with the same GMT offset that differ in the way they handle daylight savings time. For example, the state of Arizona doesn't observe daylight savings time. If you ask for the time zone IDs corresponding to GMT-7:00, you'll get back an enumeration over two time zone IDs: "America/Denver," which corresponds to Mountain Standard Time in the winter and Mountain Daylight Time in the summer, and "America/Phoenix", which corresponds to Mountain Standard Time year-round, even in the summer.

Parameters

rawOffset an offset from GMT in milliseconds, ignoring the effect of daylight savings time, if any

Returns: an enumeration object, owned by the caller

Stable:: ICU 2.4

◆ createEnumeration() [3/3]

static StringEnumeration* icu::TimeZone::createEnumeration ( const char * country )

static

Returns an enumeration over time zone IDs associated with the given country.

Some zones are affiliated with no country (e.g., "UTC"); these may also be retrieved, as a group.

Parameters

country The ISO 3166 two-letter country code, or NULL to retrieve zones not affiliated with any country.

Returns: an enumeration object, owned by the caller

Stable:: ICU 2.4

◆ createTimeZone()

static TimeZone* icu::TimeZone::createTimeZone ( const UnicodeString & ID )

static

Creates a TimeZone for the given ID.

Parameters

ID	the ID for a `TimeZone`, such as "America/Los_Angeles", or a custom ID such as "GMT-8:00".

Returns: the specified TimeZone, or a mutable clone of getUnknown() if the given ID cannot be understood or if the given ID is "Etc/Unknown". The return result is guaranteed to be non-NULL. If you require that the specific zone asked for be returned, compare the result with getUnknown() or check the ID of the return result.

Stable:: ICU 2.0

◆ createTimeZoneIDEnumeration()

static StringEnumeration* icu::TimeZone::createTimeZoneIDEnumeration	(	USystemTimeZoneType	zoneType,
		const char *	region,
		const int32_t *	rawOffset,
		UErrorCode &	ec
	)

static

Returns an enumeration over system time zone IDs with the given filter conditions.

Parameters

zoneType	The system time zone type.
region	The ISO 3166 two-letter country code or UN M.49 three-digit area code. When NULL, no filtering done by region.
rawOffset	An offset from GMT in milliseconds, ignoring the effect of daylight savings time, if any. When NULL, no filtering done by zone offset.
ec	Output param to filled in with a success or an error.

Returns: an enumeration object, owned by the caller.

Stable:: ICU 4.8

◆ detectHostTimeZone()

static TimeZone* icu::TimeZone::detectHostTimeZone ( )

static

Creates an instance of TimeZone detected from the current host system configuration.

If the host system detection routines fail, or if they specify a TimeZone or TimeZone offset which is not recognized, then the special TimeZone "Etc/Unknown" is returned.

Note that ICU4C does not change the default time zone unless TimeZone::adoptDefault(TimeZone*) or TimeZone::setDefault(const TimeZone&) is explicitly called by a user. This method does not update the current ICU's default, and may return a different TimeZone from the one returned by TimeZone::createDefault().

This function is not thread safe.

Returns: A new instance of TimeZone detected from the current host system configuration.

See also: adoptDefault; setDefault; createDefault; getUnknown

Stable:: ICU 55

◆ getCanonicalID() [1/2]

static UnicodeString& icu::TimeZone::getCanonicalID	(	const UnicodeString &	id,
		UnicodeString &	canonicalID,
		UErrorCode &	status
	)

static

Returns the canonical system timezone ID or the normalized custom time zone ID for the given time zone ID.

Parameters

id	The input time zone ID to be canonicalized.
canonicalID	Receives the canonical system time zone ID or the custom time zone ID in normalized format.
status	Receives the status. When the given time zone ID is neither a known system time zone ID nor a valid custom time zone ID, U_ILLEGAL_ARGUMENT_ERROR is set.

Returns: A reference to the result.

Stable:: ICU 4.0

◆ getCanonicalID() [2/2]

static UnicodeString& icu::TimeZone::getCanonicalID	(	const UnicodeString &	id,
		UnicodeString &	canonicalID,
		UBool &	isSystemID,
		UErrorCode &	status
	)

static

Returns the canonical system time zone ID or the normalized custom time zone ID for the given time zone ID.

Parameters

id	The input time zone ID to be canonicalized.
canonicalID	Receives the canonical system time zone ID or the custom time zone ID in normalized format.
isSystemID	Receives if the given ID is a known system time zone ID.
status	Receives the status. When the given time zone ID is neither a known system time zone ID nor a valid custom time zone ID, U_ILLEGAL_ARGUMENT_ERROR is set.

Returns: A reference to the result.

Stable:: ICU 4.0

◆ getDisplayName() [1/4]

UnicodeString& icu::TimeZone::getDisplayName ( UnicodeString & result ) const

Returns a name of this time zone suitable for presentation to the user in the default locale.

This method returns the long name, not including daylight savings. If the display name is not available for the locale, then this method returns a string in the localized GMT offset format such as GMT[+-]HH:mm.

Parameters

result the human-readable name of this time zone in the default locale.

Returns: A reference to 'result'.

Stable:: ICU 2.0

◆ getDisplayName() [2/4]

UnicodeString& icu::TimeZone::getDisplayName	(	const Locale &	locale,
		UnicodeString &	result
	)		const

Returns a name of this time zone suitable for presentation to the user in the specified locale.

This method returns the long name, not including daylight savings. If the display name is not available for the locale, then this method returns a string in the localized GMT offset format such as GMT[+-]HH:mm.

Parameters

locale	the locale in which to supply the display name.
result	the human-readable name of this time zone in the given locale or in the default locale if the given locale is not recognized.

Returns: A reference to 'result'.

Stable:: ICU 2.0

◆ getDisplayName() [3/4]

UnicodeString& icu::TimeZone::getDisplayName	(	UBool	inDaylight,
		EDisplayType	style,
		UnicodeString &	result
	)		const

Returns a name of this time zone suitable for presentation to the user in the default locale.

If the display name is not available for the locale, then this method returns a string in the localized GMT offset format such as GMT[+-]HH:mm.

Parameters

inDaylight	if true, return the daylight savings name.
style
result	the human-readable name of this time zone in the default locale.

Returns: A reference to 'result'.

Stable:: ICU 2.0

◆ getDisplayName() [4/4]

UnicodeString& icu::TimeZone::getDisplayName	(	UBool	inDaylight,
		EDisplayType	style,
		const Locale &	locale,
		UnicodeString &	result
	)		const

Returns a name of this time zone suitable for presentation to the user in the specified locale.

If the display name is not available for the locale, then this method returns a string in the localized GMT offset format such as GMT[+-]HH:mm.

Parameters

inDaylight	if true, return the daylight savings name.
style
locale	the locale in which to supply the display name.
result	the human-readable name of this time zone in the given locale or in the default locale if the given locale is not recognized.

Returns: A reference to 'result'.

Stable:: ICU 2.0

◆ getDSTSavings()

virtual int32_t icu::TimeZone::getDSTSavings ( ) const

virtual

Returns the amount of time to be added to local standard time to get local wall clock time.

The default implementation always returns 3600000 milliseconds (i.e., one hour) if this time zone observes Daylight Saving Time. Otherwise, 0 (zero) is returned.

If an underlying TimeZone implementation subclass supports historical Daylight Saving Time changes, this method returns the known latest daylight saving value.

Returns: the amount of saving time in milliseconds

Stable:: ICU 3.6

Reimplemented in icu::SimpleTimeZone.

◆ getDynamicClassID()

virtual UClassID icu::TimeZone::getDynamicClassID ( void ) const

pure virtual

Returns a unique class ID POLYMORPHICALLY.

This method is to implement a simple version of RTTI, since not all C++ compilers support genuine RTTI. Polymorphic operator==() and clone() methods call this method.

Concrete subclasses of TimeZone must use the UOBJECT_DEFINE_RTTI_IMPLEMENTATION macro from uobject.h in their implementation to provide correct RTTI information.

Returns: The class ID for this object. All objects of a given class have the same class ID. Objects of other classes have different class IDs.

Stable:: ICU 2.0

Reimplemented from icu::UObject.

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ getEquivalentID()

static const UnicodeString icu::TimeZone::getEquivalentID	(	const UnicodeString &	id,
		int32_t	index
	)

static

Returns an ID in the equivalency group that includes the given ID.

An equivalency group contains zones that have the same GMT offset and rules.

The given index must be in the range 0..n-1, where n is the value returned by countEquivalentIDs(id). For some value of 'index', the returned value will be equal to the given id. If the given id is not a valid system time zone, or if 'index' is out of range, then returns an empty string.

Parameters

id	a system time zone ID
index	a value from 0 to n-1, where n is the value returned by `countEquivalentIDs(id)`

Returns: the ID of the index-th zone in the equivalency group containing 'id', or an empty string if 'id' is not a valid system ID or 'index' is out of range

See also: countEquivalentIDs

Stable:: ICU 2.0

◆ getGMT()

static const TimeZone* icu::TimeZone::getGMT ( void )

static

The GMT (=UTC) time zone has a raw offset of zero and does not use daylight savings time.

This is a commonly used time zone.

Note: For backward compatibility reason, the ID used by the time zone returned by this method is "GMT", although the ICU's canonical ID for the GMT time zone is "Etc/GMT".

Returns: the GMT/UTC time zone.

See also: getUnknown

Stable:: ICU 2.0

◆ getID()

UnicodeString & icu::TimeZone::getID ( UnicodeString & ID ) const

inline

Fills in "ID" with the TimeZone's ID.

Parameters

ID	Receives this TimeZone's ID.

Returns: A reference to 'ID'

Stable:: ICU 2.0

Definition at line 958 of file timezone.h.

◆ getIDForWindowsID()

static UnicodeString& icu::TimeZone::getIDForWindowsID	(	const UnicodeString &	winid,
		const char *	region,
		UnicodeString &	id,
		UErrorCode &	status
	)

static

Converts a Windows time zone ID to an equivalent system time zone ID for a region.

For example, system time zone ID "America/Los_Angeles" is returned for input Windows ID "Pacific Standard Time" and region "US" (or null), "America/Vancouver" is returned for the same Windows ID "Pacific Standard Time" and region "CA".

Not all Windows time zones can be mapped to system time zones. When the input Windows time zone ID is unknown or unmappable to a system time zone, then the result will be empty, but the operation itself remains successful (no error status set on return).

This implementation utilizes Zone-Tzid mapping data. The mapping data is updated time to time. To get the latest changes, please read the ICU user guide section Updating the Time Zone Data.

Parameters

winid	A Windows time zone ID.
region	A null-terminated region code, or `NULL` if no regional preference.
id	Receives a system time zone ID. When the input Windows time zone ID is unknown or unmappable to a system time zone ID, then an empty string is set on return.
status	Receives the status.

Returns: A reference to the result (id).

See also: getWindowsID

Stable:: ICU 52

◆ getOffset() [1/3]

virtual int32_t icu::TimeZone::getOffset	(	uint8_t	era,
		int32_t	year,
		int32_t	month,
		int32_t	day,
		uint8_t	dayOfWeek,
		int32_t	millis,
		UErrorCode &	status
	)		const

pure virtual

Returns the TimeZone's adjusted GMT offset (i.e., the number of milliseconds to add to GMT to get local time in this time zone, taking daylight savings time into account) as of a particular reference date.

The reference date is used to determine whether daylight savings time is in effect and needs to be figured into the offset that is returned (in other words, what is the adjusted GMT offset in this time zone at this particular date and time?). For the time zones produced by createTimeZone(), the reference data is specified according to the Gregorian calendar, and the date and time fields are local standard time.

Note: Don't call this method. Instead, call the getOffset(UDate...) overload, which returns both the raw and the DST offset for a given time. This method is retained only for backward compatibility.

Parameters

era	The reference date's era
year	The reference date's year
month	The reference date's month (0-based; 0 is January)
day	The reference date's day-in-month (1-based)
dayOfWeek	The reference date's day-of-week (1-based; 1 is Sunday)
millis	The reference date's milliseconds in day, local standard time
status	Output param to filled in with a success or an error.

Returns: The offset in milliseconds to add to GMT to get local time.

Stable:: ICU 2.0

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

Referenced by icu::SimpleTimeZone::getOffset().

◆ getOffset() [2/3]

virtual int32_t icu::TimeZone::getOffset	(	uint8_t	era,
		int32_t	year,
		int32_t	month,
		int32_t	day,
		uint8_t	dayOfWeek,
		int32_t	milliseconds,
		int32_t	monthLength,
		UErrorCode &	status
	)		const

pure virtual

Gets the time zone offset, for current date, modified in case of daylight savings.

This is the offset to add to UTC to get local time.

Note: Don't call this method. Instead, call the getOffset(UDate...) overload, which returns both the raw and the DST offset for a given time. This method is retained only for backward compatibility.

Parameters

era	the era of the given date.
year	the year in the given date.
month	the month in the given date. Month is 0-based. e.g., 0 for January.
day	the day-in-month of the given date.
dayOfWeek	the day-of-week of the given date.
milliseconds	the millis in day in standard local time.
monthLength	the length of the given month in days.
status	Output param to filled in with a success or an error.

Returns: the offset to add to GMT to get local time.

Stable:: ICU 2.0

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ getOffset() [3/3]

virtual void icu::TimeZone::getOffset	(	UDate	date,
		UBool	local,
		int32_t &	rawOffset,
		int32_t &	dstOffset,
		UErrorCode &	ec
	)		const

virtual

Returns the time zone raw and GMT offset for the given moment in time.

Upon return, local-millis = GMT-millis + rawOffset + dstOffset. All computations are performed in the proleptic Gregorian calendar. The default implementation in the TimeZone class delegates to the 8-argument getOffset().

Parameters

date	moment in time for which to return offsets, in units of milliseconds from January 1, 1970 0:00 GMT, either GMT time or local wall time, depending on `local'.
local	if true, `date' is local wall time; otherwise it is in GMT time.
rawOffset	output parameter to receive the raw offset, that is, the offset not including DST adjustments
dstOffset	output parameter to receive the DST offset, that is, the offset to be added to `rawOffset' to obtain the total offset between local and GMT time. If DST is not in effect, this value is zero; otherwise it is a positive value, typically one hour.
ec	input-output error code

Stable:: ICU 2.8

Reimplemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ getRawOffset()

virtual int32_t icu::TimeZone::getRawOffset ( void ) const

pure virtual

Returns the TimeZone's raw GMT offset (i.e., the number of milliseconds to add to GMT to get local time, before taking daylight savings time into account).

Returns: The TimeZone's raw GMT offset.

Stable:: ICU 2.0

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ getRegion() [1/2]

static int32_t icu::TimeZone::getRegion	(	const UnicodeString &	id,
		char *	region,
		int32_t	capacity,
		UErrorCode &	status
	)

static

Gets the region code associated with the given system time zone ID.

The region code is either ISO 3166 2-letter country code or UN M.49 3-digit area code. When the time zone is not associated with a specific location, for example - "Etc/UTC", "EST5EDT", then this method returns "001" (UN M.49 area code for World).

Parameters

id	The system time zone ID.
region	Output buffer for receiving the region code.
capacity	The size of the output buffer.
status	Receives the status. When the given time zone ID is not a known system time zone ID, U_ILLEGAL_ARGUMENT_ERROR is set.

Returns: The length of the output region code.

Stable:: ICU 4.8

◆ getRegion() [2/2]

static const char16_t* icu::TimeZone::getRegion	(	const UnicodeString &	id,
		UErrorCode &	status
	)

static

Returns the region code associated with the given zone, or NULL if the zone is not known.

Parameters

id	zone id string
status	Status parameter

Returns: the region associated with the given zone

Internal:: Do not use. This API is for internal use only.

◆ getStaticClassID()

static UClassID icu::TimeZone::getStaticClassID ( void )

static

Return the class ID for this class.

This is useful only for comparing to a return value from getDynamicClassID().

Returns: The class ID for all objects of this class.

Stable:: ICU 2.0

◆ getTZDataVersion()

static const char* icu::TimeZone::getTZDataVersion ( UErrorCode & status )

static

Returns the timezone data version currently used by ICU.

Parameters

status Output param to filled in with a success or an error.

Returns: the version string, such as "2007f"

Stable:: ICU 3.8

◆ getUnknown()

static const TimeZone& icu::TimeZone::getUnknown ( )

static

Returns the "unknown" time zone.

It behaves like the GMT/UTC time zone but has the UCAL_UNKNOWN_ZONE_ID = "Etc/Unknown". createTimeZone() returns a mutable clone of this time zone if the input ID is not recognized.

Returns: the "unknown" time zone.

See also: UCAL_UNKNOWN_ZONE_ID; createTimeZone; getGMT

Stable:: ICU 49

◆ getWindowsID()

static UnicodeString& icu::TimeZone::getWindowsID	(	const UnicodeString &	id,
		UnicodeString &	winid,
		UErrorCode &	status
	)

static

Converts a system time zone ID to an equivalent Windows time zone ID.

For example, Windows time zone ID "Pacific Standard Time" is returned for input "America/Los_Angeles".

There are system time zones that cannot be mapped to Windows zones. When the input system time zone ID is unknown or unmappable to a Windows time zone, then the result will be empty, but the operation itself remains successful (no error status set on return).

This implementation utilizes Zone-Tzid mapping data. The mapping data is updated time to time. To get the latest changes, please read the ICU user guide section Updating the Time Zone Data.

Parameters

id	A system time zone ID.
winid	Receives a Windows time zone ID. When the input system time zone ID is unknown or unmappable to a Windows time zone ID, then an empty string is set on return.
status	Receives the status.

Returns: A reference to the result (winid).

See also: getIDForWindowsID

Stable:: ICU 52

◆ hasSameRules()

virtual UBool icu::TimeZone::hasSameRules ( const TimeZone & other ) const

virtual

Returns true if this zone has the same rule and offset as another zone.

That is, if this zone differs only in ID, if at all.

Parameters

other the TimeZone object to be compared with

Returns: true if the given zone is the same as this one, with the possible exception of the ID

Stable:: ICU 2.0

Reimplemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ inDaylightTime()

virtual UBool icu::TimeZone::inDaylightTime	(	UDate	date,
		UErrorCode &	status
	)		const

pure virtual

Queries if the given date is in daylight savings time in this time zone.

This method is wasteful since it creates a new GregorianCalendar and deletes it each time it is called. This is a deprecated method and provided only for Java compatibility.

Parameters

date	the given UDate.
status	Output param filled in with success/error code.

Returns: true if the given date is in daylight savings time, false, otherwise.

Deprecated:: ICU 2.4. Use Calendar::inDaylightTime() instead.

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ loadRule()

static UResourceBundle* icu::TimeZone::loadRule	(	const UResourceBundle *	top,
		const UnicodeString &	ruleid,
		UResourceBundle *	oldbundle,
		UErrorCode &	status
	)

staticprotected

Utility function.

For internally loading rule data.

Parameters

top	Top resource bundle for tz data
ruleid	ID of rule to load
oldbundle	Old bundle to reuse or NULL
status	Status parameter

Returns: either a new bundle or *oldbundle

Internal:: Do not use. This API is for internal use only.

◆ operator!=()

UBool icu::TimeZone::operator!= ( const TimeZone & that ) const

inline

Returns true if the two TimeZones are NOT equal; that is, if operator==() returns false.

Parameters

that	The TimeZone object to be compared with.

Returns: True if the given TimeZone is not equal to this TimeZone; false otherwise.

Stable:: ICU 2.0

Definition at line 463 of file timezone.h.

References icu::operator==().

◆ operator=()

TimeZone& icu::TimeZone::operator= ( const TimeZone & right )

protected

Default assignment operator.

Parameters

right the object to be copied.

Stable:: ICU 2.0

◆ operator==()

virtual UBool icu::TimeZone::operator== ( const TimeZone & that ) const

virtual

Returns true if the two TimeZones are equal.

(The TimeZone version only compares IDs, but subclasses are expected to also compare the fields they add.)

Parameters

that	The TimeZone object to be compared with.

Returns: True if the given TimeZone is equal to this TimeZone; false otherwise.

Stable:: ICU 2.0

Reimplemented in icu::SimpleTimeZone, icu::RuleBasedTimeZone, and icu::VTimeZone.

◆ setDefault()

static void icu::TimeZone::setDefault ( const TimeZone & zone )

static

Same as adoptDefault(), except that the TimeZone object passed in is NOT adopted; the caller remains responsible for deleting it.

See the thread safety note under adoptDefault().

Parameters

zone	The given timezone.

System:: Do not use unless you know what you are doing.

Stable:: ICU 2.0

◆ setID()

void icu::TimeZone::setID ( const UnicodeString & ID )

inline

Sets the TimeZone's ID to the specified value.

This doesn't affect any other fields (for example, if you say< blockquote>

.     TimeZone* foo = TimeZone::createTimeZone("America/New_York");
.     foo.setID("America/Los_Angeles");

the time zone's GMT offset and daylight-savings rules don't change to those for Los Angeles. They're still those for New York. Only the ID has changed.)

Parameters

ID	The new time zone ID.

Stable:: ICU 2.0

Definition at line 967 of file timezone.h.

References U_NAMESPACE_END.

◆ setRawOffset()

virtual void icu::TimeZone::setRawOffset ( int32_t offsetMillis )

pure virtual

Sets the TimeZone's raw GMT offset (i.e., the number of milliseconds to add to GMT to get local time, before taking daylight savings time into account).

Parameters

offsetMillis The new raw GMT offset for this time zone.

Stable:: ICU 2.0

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

◆ useDaylightTime()

virtual UBool icu::TimeZone::useDaylightTime ( void ) const

pure virtual

Queries if this time zone uses daylight savings time.

Returns: true if this time zone uses daylight savings time, false, otherwise.

Note:The default implementation of ICU TimeZone uses the tz database, which supports historic rule changes, for system time zones. With the implementation, there are time zones that used daylight savings time in the past, but no longer used currently. For example, Asia/Tokyo has never used daylight savings time since 1951. Most clients would expect that this method to return FALSE for such case. The default implementation of this method returns TRUE when the time zone uses daylight savings time in the current (Gregorian) calendar year.

In Java 7, observesDaylightTime() was added in addition to useDaylightTime(). In Java, useDaylightTime() only checks if daylight saving time is observed by the last known rule. This specification might not be what most users would expect if daylight saving time is currently observed, but not scheduled in future. In this case, Java's userDaylightTime() returns false. To resolve the issue, Java 7 added observesDaylightTime(), which takes the current rule into account. The method observesDaylightTime() was added in ICU4J for supporting API signature compatibility with JDK. In general, ICU4C also provides JDK compatible methods, but the current implementation userDaylightTime() serves the purpose (takes the current rule into account), observesDaylightTime() is not added in ICU4C. In addition to useDaylightTime(), ICU4C BasicTimeZone class (Note that TimeZone::createTimeZone(const UnicodeString &ID) always returns a BasicTimeZone) provides a series of methods allowing historic and future time zone rule iteration, so you can check if daylight saving time is observed or not within a given period.

Stable:: ICU 2.0

Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.

The documentation for this class was generated from the following file:

timezone.h

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Static Protected Member Functions

Friends

Detailed Description

Member Enumeration Documentation

◆ EDisplayType

Constructor & Destructor Documentation

◆ ~TimeZone()

◆ TimeZone() [1/3]

◆ TimeZone() [2/3]

◆ TimeZone() [3/3]

Member Function Documentation

◆ adoptDefault()

◆ clone()

◆ countEquivalentIDs()

◆ createDefault()

◆ createEnumeration() [1/3]

◆ createEnumeration() [2/3]

◆ createEnumeration() [3/3]

◆ createTimeZone()

◆ createTimeZoneIDEnumeration()

◆ detectHostTimeZone()

◆ getCanonicalID() [1/2]

◆ getCanonicalID() [2/2]

◆ getDisplayName() [1/4]

◆ getDisplayName() [2/4]

◆ getDisplayName() [3/4]

◆ getDisplayName() [4/4]

◆ getDSTSavings()

◆ getDynamicClassID()

◆ getEquivalentID()

◆ getGMT()

◆ getID()

◆ getIDForWindowsID()

◆ getOffset() [1/3]

◆ getOffset() [2/3]

◆ getOffset() [3/3]

◆ getRawOffset()

◆ getRegion() [1/2]

◆ getRegion() [2/2]

◆ getStaticClassID()

◆ getTZDataVersion()

◆ getUnknown()

◆ getWindowsID()

◆ hasSameRules()

◆ inDaylightTime()

◆ loadRule()

◆ operator!=()

◆ operator=()

◆ operator==()

◆ setDefault()

◆ setID()

◆ setRawOffset()

◆ useDaylightTime()