For details see the email "ICU4C C++ BasicTimeZone subclassing-API breaking changes" sent on 2013-Feb-5 to the icu-support mailing lists, - and ICU ticket #9648. + and ICU ticket #9648.
+ +The date format pattern "V" was introduced in ICU 3.8 (inherited from CLDR 1.5) as + a variation of pattern "z" to support time zone abbreviation format such as "PST". + The pattern "z" use a time zone abbreviation only when it is commonly used for a locale. + The pattern "V" was slightly different from pattern "z" and the pattern designates + a time zone abbreviation even it is not commonly used for a locale. For example, time + zone abbreviation "AEST" for Australian Eastern Standard Time might not be well recognized + by people in the United States. For the zone, pattern "z" does not use "AEST" (instead, use + UTC offset format "GMT+10:00, as the fallback) , while pattern "V" used to print out "AEST". + In CLDR 21, the data used for checking commonly used or not was completely removed (CLDR + ticket #4052), so the difference + between pattern "z" and "V" is no longer available since ICU 49 (based on CLDR 21 specification).
+ +In CLDR 23, the CLDR technical committee decided to reuse the semantically deprecated + pattern "V" for a different purpose. With the new specification, the date format pattern + "V" is used for short time zone IDs, such as "uslax" for zone America/Los_Angeles. ICU 51 + implements the new specification. So existing ICU users currently using custom date format + patterns with pattern "V" are suggested to change them to pattern "z".
+ +Note that the existing pattern "VVVV" for a time zone's generic location name is not + affected by the new specification and the pattern "VVVV" continues to work as same as + previous ICU releases.