TimeZone represents a time zone offset, and also figures out daylight savings. More...
#include <timezone.h>
TimeZone for the given ID. More...
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:
(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 133 of file timezone.h.
◆ EDisplayTypeEnum for use with getDisplayName.
Selector for short display name.
Selector for long display name.
Selector for short generic display name.
Selector for long generic display name.
Selector for short display name derived from time zone offset.
Selector for long display name derived from time zone offset.
Selector for short display name derived from the time zone's fallback name.
Selector for long display name derived from the time zone's fallback name.
Definition at line 675 of file timezone.h.
◆ ~TimeZone() virtual icu::TimeZone::~TimeZone ( ) virtual ◆ TimeZone() [1/3] icu::TimeZone::TimeZone ( ) protectedDefault constructor.
ID is initialized to the empty string.
Copy constructor.
Sets the default time zone (i.e., what's returned by createDefault()) to be the specified time zone.
If nullptr 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.
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.
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 an enumeration over time zone IDs associated with the given region.
Some zones are affiliated with no region (e.g., "UTC"); these may also be retrieved, as a group.
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.
Returns an enumeration over all recognized time zone IDs.
(i.e., all strings that createTimeZone() accepts)
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.
Returns an enumeration over time zone IDs associated with the given region.
Some zones are affiliated with no region (e.g., "UTC"); these may also be retrieved, as a group.
Creates a TimeZone for the given ID.
TimeZone, such as "America/Los_Angeles", or a custom ID such as "GMT-8:00".
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-nullptr. If you require that the specific zone asked for be returned, compare the result with getUnknown() or check the ID of the return result.
Returns an enumeration over system time zone IDs with the given filter conditions.
If the locale contains the timezone keyword, creates a copy of that TimeZone.
Otherwise, create the default timezone.
Returns the canonical system time zone ID or the normalized custom time zone ID for the given time zone ID.
Returns the canonical system timezone ID or the normalized custom time zone ID for the given time zone ID.
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.
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.
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.
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.
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.
Reimplemented in icu::SimpleTimeZone.
◆ getDynamicClassID() virtual UClassID icu::TimeZone::getDynamicClassID ( ) const overridepure virtualReturns 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.
Reimplemented from icu::UObject.
Implemented in icu::VTimeZone, icu::SimpleTimeZone, and icu::RuleBasedTimeZone.
◆ getEquivalentID()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.
countEquivalentIDs(id)
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 preferred time zone ID in the IANA time zone database for the given time zone ID.
There are two types of preferred IDs. The first type is the one defined in zone.tab file, such as "America/Los_Angeles". The second types is the one defined for zones not associated with a specific region, but not defined with "Link" syntax such as "Etc/GMT+10".
Note: For most of valid time zone IDs, this method returns an ID same as getCanonicalID(). getCanonicalID() is based on canonical time zone IDs defined in Unicode CLDR. These canonical time zone IDs in CLDR were based on very old version of the time zone database. In the IANA time zone database, some IDs were updated since then. This API returns a newer time zone ID. For example, CLDR defines "Asia/Calcutta" as the canonical time zone ID. This method returns "Asia/Kolkata" instead.
"Etc/Unknown" is a special time zone ID defined by CLDR. There are no corresponding zones in the IANA time zone database. Therefore, this API returns U_ILLEGAL_ARGUMENT_ERROR when the input ID is "Etc/Unknown".
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.
nullptr 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.
id).
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().
Reimplemented in icu::VTimeZone, icu::SimpleTimeZone, and icu::RuleBasedTimeZone.
◆ 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 millis, UErrorCode & status ) const pure virtualReturns 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.
Implemented in icu::VTimeZone, icu::SimpleTimeZone, and icu::RuleBasedTimeZone.
◆ getOffset() [3/3] 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 virtualGets 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.
Implemented in icu::SimpleTimeZone, icu::VTimeZone, and icu::RuleBasedTimeZone.
◆ getRawOffset() virtual int32_t icu::TimeZone::getRawOffset ( ) const pure virtual ◆ getRegion() [1/2] static int32_t icu::TimeZone::getRegion ( const UnicodeString & id, char * region, int32_t capacity, UErrorCode & status ) staticGets 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).
Returns the region code associated with the given zone, or nullptr if the zone is not known.
Return the class ID for this class.
This is useful only for comparing to a return value from getDynamicClassID().
Returns the timezone data version currently used by ICU.
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.
winid).
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.
TimeZone object to be compared with
Reimplemented in icu::VTimeZone, icu::SimpleTimeZone, and icu::RuleBasedTimeZone.
◆ inDaylightTime()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.
Implemented in icu::VTimeZone, icu::SimpleTimeZone, and icu::RuleBasedTimeZone.
◆ loadRule()Utility function.
For internally loading rule data.
Default assignment operator.
Same as adoptDefault(), except that the TimeZone object passed in is NOT adopted; the caller remains responsible for deleting it.
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.)
Definition at line 1056 of file timezone.h.
◆ setRawOffset() virtual void icu::TimeZone::setRawOffset ( int32_t offsetMillis ) pure virtual ◆ useDaylightTime() virtual UBool icu::TimeZone::useDaylightTime ( ) const pure virtualQueries if this time zone uses daylight savings time.
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.
Implemented in icu::VTimeZone, icu::SimpleTimeZone, and icu::RuleBasedTimeZone.
The documentation for this class was generated from the following file:
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