darcs patch: Figure out timezone offset from timezone name

[David Leuschner]

>> Which time zone is used at what time indeed changes frequently but I am
>> not aware of any case where the meaning of a time zone _name_ changed.
>
> What's your source for time-zone names?

I just realised I forgot to add a comment in the patch.  It's the table
from the PostgreSQL manual

http://www.postgresql.org/docs/8.1/static/datetime-keywords.html

Cheers,
 
   David

-- 
David Leuschner
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