> > The browser may not know the setting, or may not tell it to you,
> > or you might not be able to make any sense of what it says
> > (timezone names are hardly standardized).
>
> Well that's true. Except for numeric offsets.
Offsets aren't good enough due to changing DST rules. A current
offset may not be the right one for a stamp from 6 hours ago, and the
DST changeover point may be different for a stamp from a year ago.
