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 // © 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 /*************************************************************************
 * Copyright (c) 1997-2016, International Business Machines Corporation
 * and others. All Rights Reserved.
 **************************************************************************
 *
 * File TIMEZONE.H
 *
 * Modification History:
 *
 *   Date        Name        Description
 *   04/21/97    aliu        Overhauled header.
 *   07/09/97    helena      Changed createInstance to createDefault.
 *   08/06/97    aliu        Removed dependency on internal header for Hashtable.
 *   08/10/98    stephen        Changed getDisplayName() API conventions to match
 *   08/19/98    stephen        Changed createTimeZone() to never return 0
 *   09/02/98    stephen        Sync to JDK 1.2 8/31
 *                            - Added getOffset(... monthlen ...)
 *                            - Added hasSameRules()
 *   09/15/98    stephen        Added getStaticClassID
 *   12/03/99    aliu        Moved data out of static table into icudata.dll.
 *                           Hashtable replaced by new static data structures.
 *   12/14/99    aliu        Made GMT public.
 *   08/15/01    grhoten     Made GMT private and added the getGMT() function
 **************************************************************************
 */
 
 #ifndef TIMEZONE_H
 #define TIMEZONE_H
 
 #include "unicode/utypes.h"
 
 #if U_SHOW_CPLUSPLUS_API
 
 /**
  * \file 
  * \brief C++ API: TimeZone object
  */
 
 #if !UCONFIG_NO_FORMATTING
 
 #include "unicode/uobject.h"
 #include "unicode/unistr.h"
 #include "unicode/ures.h"
 #include "unicode/ucal.h"
 
 U_NAMESPACE_BEGIN
 
 class StringEnumeration;
 
 /**
  *
  * <code>TimeZone</code> represents a time zone offset, and also figures out daylight
  * savings.
  *
  * <p>
  * Typically, you get a <code>TimeZone</code> using <code>createDefault</code>
  * which creates a <code>TimeZone</code> based on the time zone where the program
  * is running. For example, for a program running in Japan, <code>createDefault</code>
  * creates a <code>TimeZone</code> object based on Japanese Standard Time.
  *
  * <p>
  * You can also get a <code>TimeZone</code> using <code>createTimeZone</code> 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 <code>TimeZone</code> object
  * with:
  * \htmlonly<blockquote>\endhtmlonly
  * <pre>
  * TimeZone *tz = TimeZone::createTimeZone("America/Los_Angeles");
  * </pre>
  * \htmlonly</blockquote>\endhtmlonly
  * You can use the <code>createEnumeration</code> method to iterate through
  * all the supported time zone IDs, or the <code>getCanonicalID</code> method to check
  * if a time zone ID is supported or not.  You can then choose a
  * supported ID to get a <code>TimeZone</code>.
  * 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:
  *
  * \htmlonly<blockquote>\endhtmlonly
  * <pre>
  * GMT[+|-]hh[[:]mm]
  * </pre>
  * \htmlonly</blockquote>\endhtmlonly
  *
  * For example, you might specify GMT+14:00 as a custom
  * time zone ID.  The <code>TimeZone</code> 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,
  * <code>getCanonicalID</code> 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:
  * <ul>
  *    <li>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).</li>
  *    <li>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).</li>
  *    <li>An ID.  This is a text string that uniquely identifies the time zone.</li>
  * </ul>
  *
  * (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.)
  * <P>
  * 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.
  * <P>
  * 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().
  * <P>
  * 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").
  */
 class U_I18N_API TimeZone : public UObject {
 public:
     /**
      * @stable ICU 2.0
      */
     virtual ~TimeZone();
 
     /**
      * Returns the "unknown" time zone.
      * It behaves like the GMT/UTC time zone but has the
      * <code>UCAL_UNKNOWN_ZONE_ID</code> = "Etc/Unknown".
      * createTimeZone() returns a mutable clone of this time zone if the input ID is not recognized.
      *
      * @return the "unknown" time zone.
      * @see UCAL_UNKNOWN_ZONE_ID
      * @see createTimeZone
      * @see getGMT
      * @stable ICU 49
      */
     static const TimeZone& U_EXPORT2 getUnknown();
 
     /**
      * 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.
      *
      * <p>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".
      *
      * @return the GMT/UTC time zone.
      * @see getUnknown
      * @stable ICU 2.0
      */
     static const TimeZone* U_EXPORT2 getGMT();
 
     /**
      * Creates a <code>TimeZone</code> for the given ID.
      * @param ID the ID for a <code>TimeZone</code>, such as "America/Los_Angeles",
      * or a custom ID such as "GMT-8:00".
      * @return the specified <code>TimeZone</code>, 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.
      * @stable ICU 2.0
      */
     static TimeZone* U_EXPORT2 createTimeZone(const UnicodeString& ID);
 
     /**
      * Returns an enumeration over system time zone IDs with the given
      * filter conditions.
      * @param zoneType      The system time zone type.
      * @param region        The ISO 3166 two-letter country code or UN M.49
      *                      three-digit area code. When nullptr, no filtering
      *                      done by region. 
      * @param rawOffset     An offset from GMT in milliseconds, ignoring
      *                      the effect of daylight savings time, if any.
      *                      When nullptr, no filtering done by zone offset.
      * @param ec            Output param to filled in with a success or
      *                      an error.
      * @return an enumeration object, owned by the caller.
      * @stable ICU 4.8
      */
     static StringEnumeration* U_EXPORT2 createTimeZoneIDEnumeration(
         USystemTimeZoneType zoneType,
         const char* region,
         const int32_t* rawOffset,
         UErrorCode& ec);
 
 #ifndef U_HIDE_DEPRECATED_API
     /**
      * Returns an enumeration over all recognized time zone IDs. (i.e.,
      * all strings that createTimeZone() accepts)
      *
      * @return an enumeration object, owned by the caller.
      * @deprecated ICU 70 Use createEnumeration(UErrorCode&) instead.
      */
     static StringEnumeration* U_EXPORT2 createEnumeration();
 #endif  // U_HIDE_DEPRECATED_API
 
     /**
      * Returns an enumeration over all recognized time zone IDs. (i.e.,
      * all strings that createTimeZone() accepts)
      *
      * @param status Receives the status.
      * @return an enumeration object, owned by the caller.
      * @stable ICU 70
      */
     static StringEnumeration* U_EXPORT2 createEnumeration(UErrorCode& status);
 
 #ifndef U_HIDE_DEPRECATED_API
     /**
      * 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.
      *
      * @param rawOffset an offset from GMT in milliseconds, ignoring
      * the effect of daylight savings time, if any
      * @return an enumeration object, owned by the caller
      * @deprecated ICU 70 Use createEnumerationForRawOffset(int32_t,UErrorCode&) instead.
      */
     static StringEnumeration* U_EXPORT2 createEnumeration(int32_t rawOffset);
 #endif  // U_HIDE_DEPRECATED_API
 
     /**
      * 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.
      *
      * @param rawOffset an offset from GMT in milliseconds, ignoring
      * the effect of daylight savings time, if any
      * @param status Receives the status.
      * @return an enumeration object, owned by the caller
      * @stable ICU 70
      */
     static StringEnumeration* U_EXPORT2 createEnumerationForRawOffset(int32_t rawOffset, UErrorCode& status);
 
 #ifndef U_HIDE_DEPRECATED_API
     /**
      * 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.
      *
      * @param region The ISO 3166 two-letter country code, or nullptr to
      * retrieve zones not affiliated with any region.
      * @return an enumeration object, owned by the caller
      * @deprecated ICU 70 Use createEnumerationForRegion(const char*,UErrorCode&) instead.
      */
     static StringEnumeration* U_EXPORT2 createEnumeration(const char* region);
 #endif  // U_HIDE_DEPRECATED_API
 
     /**
      * 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.
      *
      * @param region The ISO 3166 two-letter country code, or nullptr to
      * retrieve zones not affiliated with any region.
      * @param status Receives the status.
      * @return an enumeration object, owned by the caller
      * @stable ICU 70
      */
     static StringEnumeration* U_EXPORT2 createEnumerationForRegion(const char* region, UErrorCode& status);
 
     /**
      * 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.
      *
      * <p>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.
      * @param id a system time zone ID
      * @return the number of zones in the equivalency group containing
      * 'id', or zero if 'id' is not a valid system ID
      * @see #getEquivalentID
      * @stable ICU 2.0
      */
     static int32_t U_EXPORT2 countEquivalentIDs(const UnicodeString& id);
 
     /**
      * 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.
      *
      * <p>The given index must be in the range 0..n-1, where n is the
      * value returned by <code>countEquivalentIDs(id)</code>.  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.
      * @param id a system time zone ID
      * @param index a value from 0 to n-1, where n is the value
      * returned by <code>countEquivalentIDs(id)</code>
      * @return 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 #countEquivalentIDs
      * @stable ICU 2.0
      */
     static const UnicodeString U_EXPORT2 getEquivalentID(const UnicodeString& id,
                                                int32_t index);
 
     /**
      * 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()`.
      *
      * <p>This function is not thread safe.</p>
      *
      * @return  A new instance of TimeZone detected from the current host system
      *          configuration.
      * @see adoptDefault
      * @see setDefault
      * @see createDefault
      * @see getUnknown
      * @stable ICU 55
      */
     static TimeZone* U_EXPORT2 detectHostTimeZone();
 
     /**
      * 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.
      *
      * @return   A default TimeZone. Clients are responsible for deleting the time zone
      *           object returned.
      * @see getUnknown
      * @stable ICU 2.0
      */
     static TimeZone* U_EXPORT2 createDefault();
 
 #ifndef U_HIDE_INTERNAL_API
     /**
      * If the locale contains the timezone keyword, creates a copy of that TimeZone.
      * Otherwise, create the default timezone.
      *
      * @param locale a locale which may contains 'timezone' keyword/value.
      * @return   A TimeZone. Clients are responsible for deleting the time zone
      *           object returned.
      * @internal
      */
     static TimeZone* U_EXPORT2 forLocaleOrDefault(const Locale& locale);
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * 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.
      *
      * @param zone  A pointer to the new TimeZone object to use as the default.
      * @stable ICU 2.0
      */
     static void U_EXPORT2 adoptDefault(TimeZone* zone);
 
 #ifndef U_HIDE_SYSTEM_API
     /**
      * Same as adoptDefault(), except that the TimeZone object passed in is NOT adopted;
      * the caller remains responsible for deleting it.
      *
      * @param zone  The given timezone.
      * @system
      * @stable ICU 2.0
      */
     static void U_EXPORT2 setDefault(const TimeZone& zone);
 #endif  /* U_HIDE_SYSTEM_API */
 
     /**
      * Returns the timezone data version currently used by ICU.
      * @param status Output param to filled in with a success or an error.
      * @return the version string, such as "2007f"
      * @stable ICU 3.8
      */
     static const char* U_EXPORT2 getTZDataVersion(UErrorCode& status);
 
     /**
      * Returns the canonical system timezone ID or the normalized
      * custom time zone ID for the given time zone ID.
      * @param id            The input time zone ID to be canonicalized.
      * @param canonicalID   Receives the canonical system time zone ID
      *                      or the custom time zone ID in normalized format.
      * @param 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.
      * @return A reference to the result.
      * @stable ICU 4.0
      */
     static UnicodeString& U_EXPORT2 getCanonicalID(const UnicodeString& id,
         UnicodeString& canonicalID, UErrorCode& status);
 
     /**
      * Returns the canonical system time zone ID or the normalized
      * custom time zone ID for the given time zone ID.
      * @param id            The input time zone ID to be canonicalized.
      * @param canonicalID   Receives the canonical system time zone ID
      *                      or the custom time zone ID in normalized format.
      * @param isSystemID    Receives if the given ID is a known system
      *                      time zone ID.
      * @param 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.
      * @return A reference to the result.
      * @stable ICU 4.0
      */
     static UnicodeString& U_EXPORT2 getCanonicalID(const UnicodeString& id,
         UnicodeString& canonicalID, UBool& isSystemID, UErrorCode& status);
 
 
     /**
      * 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".
      *
      * <p>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.
      * <p> "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".
      *
      * @param id        The input time zone ID.
      * @param ianaID    Receives the preferred time zone ID in the IANA time zone database. When
      *                  the given time zone ID is not a known time zone ID, this method sets an
      *                  invalid (bogus) string.
      * @param status    Receives the status.  When the given time zone ID is not a known time zone
      *                  ID, U_ILLEGAL_ARGUMENT_ERROR is set.
      * @return  A reference to the result.
      * @stable ICU 74
      */
     static UnicodeString& U_EXPORT2 getIanaID(const UnicodeString&id, UnicodeString& ianaID,
         UErrorCode& status);
 
     /**
     * 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".
     *
     * <p>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).
     *
     * <p>This implementation utilizes <a href="http://unicode.org/cldr/charts/supplemental/zone_tzid.html">
     * Zone-Tzid mapping data</a>. The mapping data is updated time to time. To get the latest changes,
     * please read the ICU user guide section <a href="https://unicode-org.github.io/icu/userguide/datetime/timezone#updating-the-time-zone-data">
     * Updating the Time Zone Data</a>.
     *
     * @param id        A system time zone ID.
     * @param 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.
     * @param status    Receives the status.
     * @return          A reference to the result (<code>winid</code>).
     * @see getIDForWindowsID
     *
     * @stable ICU 52
     */
     static UnicodeString& U_EXPORT2 getWindowsID(const UnicodeString& id,
         UnicodeString& winid, UErrorCode& status);
 
     /**
     * 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 <code>null</code>),
     * "America/Vancouver" is returned for the same Windows ID "Pacific Standard Time" and
     * region "CA".
     *
     * <p>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).
     *
     * <p>This implementation utilizes <a href="http://unicode.org/cldr/charts/supplemental/zone_tzid.html">
     * Zone-Tzid mapping data</a>. The mapping data is updated time to time. To get the latest changes,
     * please read the ICU user guide section <a href="https://unicode-org.github.io/icu/userguide/datetime/timezone#updating-the-time-zone-data">
     * Updating the Time Zone Data</a>.
     *
     * @param winid     A Windows time zone ID.
     * @param region    A NUL-terminated region code, or <code>nullptr</code> if no regional preference.
     * @param 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.
     * @param status    Receives the status.
     * @return          A reference to the result (<code>id</code>).
     * @see getWindowsID
     *
     * @stable ICU 52
     */
     static UnicodeString& U_EXPORT2 getIDForWindowsID(const UnicodeString& winid, const char* region,
         UnicodeString& id, UErrorCode& status);
 
     /**
      * 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.)
      *
      * @param that  The TimeZone object to be compared with.
      * @return      true if the given TimeZone is equal to this TimeZone; false
      *              otherwise.
      * @stable ICU 2.0
      */
     virtual bool operator==(const TimeZone& that) const;
 
     /**
      * Returns true if the two TimeZones are NOT equal; that is, if operator==() returns
      * false.
      *
      * @param that  The TimeZone object to be compared with.
      * @return      true if the given TimeZone is not equal to this TimeZone; false
      *              otherwise.
      * @stable ICU 2.0
      */
     bool operator!=(const TimeZone& that) const {return !operator==(that);}
 
     /**
      * 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.
      *
      * <p>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.
      *
      * @param era        The reference date's era
      * @param year       The reference date's year
      * @param month      The reference date's month (0-based; 0 is January)
      * @param day        The reference date's day-in-month (1-based)
      * @param dayOfWeek  The reference date's day-of-week (1-based; 1 is Sunday)
      * @param millis     The reference date's milliseconds in day, local standard time
      * @param status     Output param to filled in with a success or an error.
      * @return           The offset in milliseconds to add to GMT to get local time.
      * @stable ICU 2.0
      */
     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;
 
     /**
      * 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.
      *
      * <p>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.
      *
      * @param era the era of the given date.
      * @param year the year in the given date.
      * @param month the month in the given date.
      * Month is 0-based. e.g., 0 for January.
      * @param day the day-in-month of the given date.
      * @param dayOfWeek the day-of-week of the given date.
      * @param milliseconds the millis in day in <em>standard</em> local time.
      * @param monthLength the length of the given month in days.
      * @param status     Output param to filled in with a success or an error.
      * @return the offset to add *to* GMT to get local time.
      * @stable ICU 2.0
      */
     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;
 
     /**
      * 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().
      *
      * @param 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'.
      * @param local if true, `date' is local wall time; otherwise it
      * is in GMT time.
      * @param rawOffset output parameter to receive the raw offset, that
      * is, the offset not including DST adjustments
      * @param 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.
      * @param ec input-output error code
      *
      * @stable ICU 2.8
      */
     virtual void getOffset(UDate date, UBool local, int32_t& rawOffset,
                            int32_t& dstOffset, UErrorCode& ec) const;
 
     /**
      * 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).
      *
      * @param offsetMillis  The new raw GMT offset for this time zone.
      * @stable ICU 2.0
      */
     virtual void setRawOffset(int32_t offsetMillis) = 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).
      *
      * @return   The TimeZone's raw GMT offset.
      * @stable ICU 2.0
      */
     virtual int32_t getRawOffset() const = 0;
 
     /**
      * Fills in "ID" with the TimeZone's ID.
      *
      * @param ID  Receives this TimeZone's ID.
      * @return    A reference to 'ID'
      * @stable ICU 2.0
      */
     UnicodeString& getID(UnicodeString& ID) const;
 
     /**
      * Sets the TimeZone's ID to the specified value.  This doesn't affect any other
      * fields (for example, if you say<
      * blockquote><pre>
      * .     TimeZone* foo = TimeZone::createTimeZone("America/New_York");
      * .     foo.setID("America/Los_Angeles");
      * </pre>\htmlonly</blockquote>\endhtmlonly
      * 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.)
      *
      * @param ID  The new time zone ID.
      * @stable ICU 2.0
      */
     void setID(const UnicodeString& ID);
 
     /**
      * Enum for use with getDisplayName
      * @stable ICU 2.4
      */
     enum EDisplayType {
         /**
          * Selector for short display name
          * @stable ICU 2.4
          */
         SHORT = 1,
         /**
          * Selector for long display name
          * @stable ICU 2.4
          */
         LONG,
         /**
          * Selector for short generic display name
          * @stable ICU 4.4
          */
         SHORT_GENERIC,
         /**
          * Selector for long generic display name
          * @stable ICU 4.4
          */
         LONG_GENERIC,
         /**
          * Selector for short display name derived
          * from time zone offset
          * @stable ICU 4.4
          */
         SHORT_GMT,
         /**
          * Selector for long display name derived
          * from time zone offset
          * @stable ICU 4.4
          */
         LONG_GMT,
         /**
          * Selector for short display name derived
          * from the time zone's fallback name
          * @stable ICU 4.4
          */
         SHORT_COMMONLY_USED,
         /**
          * Selector for long display name derived
          * from the time zone's fallback name
          * @stable ICU 4.4
          */
         GENERIC_LOCATION
     };
 
     /**
      * 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 <code>GMT[+-]HH:mm</code>.
      * @param result the human-readable name of this time zone in the default locale.
      * @return       A reference to 'result'.
      * @stable ICU 2.0
      */
     UnicodeString& getDisplayName(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 <code>GMT[+-]HH:mm</code>.
      * @param locale the locale in which to supply the display name.
      * @param 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.
      * @return       A reference to 'result'.
      * @stable ICU 2.0
      */
     UnicodeString& getDisplayName(const Locale& locale, 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 <code>GMT[+-]HH:mm</code>.
      * @param inDaylight if true, return the daylight savings name.
      * @param style
      * @param result the human-readable name of this time zone in the default locale.
      * @return       A reference to 'result'.
      * @stable ICU 2.0
      */
     UnicodeString& getDisplayName(UBool inDaylight, EDisplayType style, 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 <code>GMT[+-]HH:mm</code>.
      * @param inDaylight if true, return the daylight savings name.
      * @param style
      * @param locale the locale in which to supply the display name.
      * @param 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.
      * @return       A reference to 'result'.
      * @stable ICU 2.0
      */
     UnicodeString& getDisplayName(UBool inDaylight, EDisplayType style, const Locale& locale, UnicodeString& result) const;
     
     /**
      * Queries if this time zone uses daylight savings time.
      * @return true if this time zone uses daylight savings time,
      * false, otherwise.
      * <p><strong>Note:</strong>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 <code>false</code> for such case.
      * The default implementation of this method returns <code>true</code>
      * when the time zone uses daylight savings time in the current
      * (Gregorian) calendar year.
      * <p>In Java 7, <code>observesDaylightTime()</code> was added in
      * addition to <code>useDaylightTime()</code>. In Java, <code>useDaylightTime()</code>
      * 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 <code>userDaylightTime()</code> returns
      * <code>false</code>. To resolve the issue, Java 7 added <code>observesDaylightTime()</code>,
      * which takes the current rule into account. The method <code>observesDaylightTime()</code>
      * was added in ICU4J for supporting API signature compatibility with JDK.
      * In general, ICU4C also provides JDK compatible methods, but the current
      * implementation <code>userDaylightTime()</code> serves the purpose
      * (takes the current rule into account), <code>observesDaylightTime()</code>
      * is not added in ICU4C. In addition to <code>useDaylightTime()</code>, ICU4C
      * <code>BasicTimeZone</code> class (Note that <code>TimeZone::createTimeZone(const UnicodeString &ID)</code>
      * always returns a <code>BasicTimeZone</code>) 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
      */
     virtual UBool useDaylightTime() const = 0;
 
 #ifndef U_FORCE_HIDE_DEPRECATED_API
     /**
      * 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.
      *
      * @param date the given UDate.
      * @param status Output param filled in with success/error code.
      * @return true if the given date is in daylight savings time,
      * false, otherwise.
      * @deprecated ICU 2.4. Use Calendar::inDaylightTime() instead.
      */
     virtual UBool inDaylightTime(UDate date, UErrorCode& status) const = 0;
 #endif  // U_FORCE_HIDE_DEPRECATED_API
 
     /**
      * 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.
      * @param other the <code>TimeZone</code> object to be compared with
      * @return true if the given zone is the same as this one,
      * with the possible exception of the ID
      * @stable ICU 2.0
      */
     virtual UBool hasSameRules(const TimeZone& other) const;
 
     /**
      * Clones TimeZone objects polymorphically. Clients are responsible for deleting
      * the TimeZone object cloned.
      *
      * @return   A new copy of this TimeZone object.
      * @stable ICU 2.0
      */
     virtual TimeZone* clone() const = 0;
 
     /**
      * Return the class ID for this class.  This is useful only for
      * comparing to a return value from getDynamicClassID().
      * @return The class ID for all objects of this class.
      * @stable ICU 2.0
      */
     static UClassID U_EXPORT2 getStaticClassID();
 
     /**
      * 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.
      * <P>
      * Concrete subclasses of TimeZone must use the UOBJECT_DEFINE_RTTI_IMPLEMENTATION
      *  macro from uobject.h in their implementation to provide correct RTTI information.
      * @return   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
      */
     virtual UClassID getDynamicClassID() const override = 0;
 
     /**
      * Returns the amount of time to be added to local standard time
      * to get local wall clock time.
      * <p>
      * The default implementation always returns 3600000 milliseconds
      * (i.e., one hour) if this time zone observes Daylight Saving
      * Time. Otherwise, 0 (zero) is returned.
      * <p>
      * If an underlying TimeZone implementation subclass supports
      * historical Daylight Saving Time changes, this method returns
      * the known latest daylight saving value.
      *
      * @return the amount of saving time in milliseconds
      * @stable ICU 3.6
      */
     virtual int32_t getDSTSavings() const;
 
     /**
      * 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).
      * 
      * @param id            The system time zone ID.
      * @param region        Output buffer for receiving the region code.
      * @param capacity      The size of the output buffer.
      * @param status        Receives the status.  When the given time zone ID
      *                      is not a known system time zone ID,
      *                      U_ILLEGAL_ARGUMENT_ERROR is set.
      * @return The length of the output region code.
      * @stable ICU 4.8 
      */ 
     static int32_t U_EXPORT2 getRegion(const UnicodeString& id, 
         char *region, int32_t capacity, UErrorCode& status); 
 
 protected:
 
     /**
      * Default constructor.  ID is initialized to the empty string.
      * @stable ICU 2.0
      */
     TimeZone();
 
     /**
      * Construct a TimeZone with a given ID.
      * @param id a system time zone ID
      * @stable ICU 2.0
      */
     TimeZone(const UnicodeString &id);
 
     /**
      * Copy constructor.
      * @param source the object to be copied.
      * @stable ICU 2.0
      */
     TimeZone(const TimeZone& source);
 
     /**
      * Default assignment operator.
      * @param right the object to be copied.
      * @stable ICU 2.0
      */
     TimeZone& operator=(const TimeZone& right);
 
 #ifndef U_HIDE_INTERNAL_API
     /**
      * Utility function. For internally loading rule data.
      * @param top Top resource bundle for tz data
      * @param ruleid ID of rule to load
      * @param oldbundle Old bundle to reuse or nullptr
      * @param status Status parameter
      * @return either a new bundle or *oldbundle
      * @internal
      */
     static UResourceBundle* loadRule(const UResourceBundle* top, const UnicodeString& ruleid, UResourceBundle* oldbundle, UErrorCode&status);
 #endif  /* U_HIDE_INTERNAL_API */
 
 private:
     friend class ZoneMeta;
 
 
     static TimeZone*        createCustomTimeZone(const UnicodeString&); // Creates a time zone based on the string.
 
     /**
      * Finds the given ID in the Olson tzdata. If the given ID is found in the tzdata,
      * returns the pointer to the ID resource. This method is exposed through ZoneMeta class
      * for ICU internal implementation and useful for building hashtable using a time zone
      * ID as a key.
      * @param id zone id string
      * @return the pointer of the ID resource, or nullptr.
      */
     static const char16_t* findID(const UnicodeString& id);
 
     /**
      * Resolve a link in Olson tzdata.  When the given id is known and it's not a link,
      * the id itself is returned.  When the given id is known and it is a link, then
      * dereferenced zone id is returned.  When the given id is unknown, then it returns
      * nullptr.
      * @param id zone id string
      * @return the dereferenced zone or nullptr
      */
     static const char16_t* dereferOlsonLink(const UnicodeString& id);
 
     /**
      * Returns the region code associated with the given zone,
      * or nullptr if the zone is not known.
      * @param id zone id string
      * @return the region associated with the given zone
      */
     static const char16_t* getRegion(const UnicodeString& id);
 
   public:
 #ifndef U_HIDE_INTERNAL_API
     /**
      * Returns the region code associated with the given zone,
      * or nullptr if the zone is not known.
      * @param id zone id string
      * @param status Status parameter
      * @return the region associated with the given zone
      * @internal
      */
     static const char16_t* getRegion(const UnicodeString& id, UErrorCode& status);
 #endif  /* U_HIDE_INTERNAL_API */
 
   private:
     /**
      * Parses the given custom time zone identifier
      * @param id id A string of the form GMT[+-]hh:mm, GMT[+-]hhmm, or
      * GMT[+-]hh.
      * @param sign Receives parsed sign, 1 for positive, -1 for negative.
      * @param hour Receives parsed hour field
      * @param minute Receives parsed minute field
      * @param second Receives parsed second field
      * @return Returns true when the given custom id is valid.
      */
     static UBool parseCustomID(const UnicodeString& id, int32_t& sign, int32_t& hour,
         int32_t& minute, int32_t& second);
 
     /**
      * Parse a custom time zone identifier and return the normalized
      * custom time zone identifier for the given custom id string.
      * @param id a string of the form GMT[+-]hh:mm, GMT[+-]hhmm, or
      * GMT[+-]hh.
      * @param normalized Receives the normalized custom ID
      * @param status Receives the status.  When the input ID string is invalid,
      * U_ILLEGAL_ARGUMENT_ERROR is set.
      * @return The normalized custom id string.
     */
     static UnicodeString& getCustomID(const UnicodeString& id, UnicodeString& normalized,
         UErrorCode& status);
 
     /**
      * Returns the normalized custom time zone ID for the given offset fields.
      * @param hour offset hours
      * @param min offset minutes
      * @param sec offset seconds
      * @param negative sign of the offset, true for negative offset.
      * @param id Receives the format result (normalized custom ID)
      * @return The reference to id
      */
     static UnicodeString& formatCustomID(int32_t hour, int32_t min, int32_t sec,
         UBool negative, UnicodeString& id);
 
     UnicodeString           fID;    // this time zone's ID
 
     friend class TZEnumeration;
 };
 
 
 // -------------------------------------
 
 inline UnicodeString&
 TimeZone::getID(UnicodeString& ID) const
 {
     ID = fID;
     return ID;
 }
 
 // -------------------------------------
 
 inline void
 TimeZone::setID(const UnicodeString& ID)
 {
     fID = ID;
 }
 U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif //_TIMEZONE
 //eof

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