DateTimeZone shouldn't have reader/writer parts in the abstract API.

[GoogleCodeExporter]

Third parties should be able to implement their own time zone providers and 
time zones. Currently the read/write part prohibits this, as it uses internal 
types.

Given that the read/write format of time zones is really 
implementation-specific, it shouldn't be part of the abstract API. The current 
format is only used for TZDB, which should be made explicit.

Original issue reported on code.google.com by jonathan.skeet on 23 Jun 2012 at 7:00