Javadocs on java.text.SimpleDateFormat state the following on the "z" pattern letter:
z Time zone General time zone Pacific Standard Time; PST; GMT-08:00
General time zone: Time zones are interpreted as text if they have names. For time zones representing a GMT offset value, the following syntax is used ...
Question is - "if they have names" ... where does it get these names from? I have seen in one environment JST coming up as "JST" and in another coming up as "GMT+9"
The Timezone names are embedded in the JVM. They come from the tz database maintained by Arthur David Olson. Disparities between timezone names are caused by JVMs using different versions of the tz database. Sun provides a Timezone updater tool for its JVMs which you can use to update the timezone name definitions. Of course its always better to use the latest JVM update, but this is not always an option.
It should support time zone display names as defined by the LDML
(Unicode Locale Data Markup Language ) specification.
You will find all the names in Time Zone Localization, especially in "aliases"