For example, people in the United States refer the zone used by the east part of North America as "Eastern Time". The tz database contains multiple time zones "America/New_York", "America/Detroit", "America/Montreal" and some others that belong to "Eastern Time". However, assigning different display names to these time zones does not make much sense for most of people.
In CLDR (which uses LDML for representing locale data), the display name "Eastern Time" is stored as long generic display name of a meta zone identified by the ID "America_Eastern". Then, there is another table maintaining the historic mapping to meta zones for each time zone. The time zones in the above example ("America/New_York", "America/Detroit"...) are mapped to the meta zone "America_Eastern".
Sometimes, a time zone is mapped to a different time zone in the past. For example, "America/Indiana/Knox" had been moving "Eastern Time" and "Central Time" back and forth. Therefore, it is necessary that time zone to meta zones mapping data are stored by date range.
Note:
{@link TimeZoneFormat} assumes an instance of TimeZoneNames is immutable. If you want to provideyour own TimeZoneNames implementation and use it with {@link TimeZoneFormat}, you must follow the contract.
The methods in this class assume that time zone IDs are already canonicalized. For example, you may not get proper result returned by a method with time zone ID "America/Indiana/Indianapolis", because it's not a canonical time zone ID (the canonical time zone ID for the time zone is "America/Indianapolis". See {@link TimeZone#getCanonicalID(String)} about ICU canonical time zone IDs.
In CLDR, most of time zone display names except location names are provided through meta zones. But a time zone may have a specific name that is not shared with other time zones. For example, time zone "Europe/London" has English long name for standard time "Greenwich Mean Time", which is also shared with other time zones. However, the long name for daylight saving time is "British Summer Time", which is only used for "Europe/London".
{@link #getTimeZoneDisplayName(String,NameType)} is designed for accessing a name only used by a single time zone.But is not necessarily mean that a subclass implementation use the same model with CLDR. A subclass implementation may provide time zone names only through {@link #getTimeZoneDisplayName(String,NameType)}, or only through {@link #getMetaZoneDisplayName(String,NameType)}, or both.
The default TimeZoneNames implementation returned by {@link #getInstance(ULocale)} uses the locale dataimported from CLDR. In CLDR, set of meta zone IDs and mappings between zone IDs and meta zone IDs are shared by all locales. Therefore, the behavior of {@link #getAvailableMetaZoneIDs()}, {@link #getAvailableMetaZoneIDs(String)}, {@link #getMetaZoneID(String,long)}, and {@link #getReferenceZoneID(String,String)} won't be changed no matterwhat locale is used for getting an instance of TimeZoneNames.
@draft ICU 49
@provisional This API might change or be removed in a future release.
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