zoo timezone bug fix

[Gordon Burditt]

>I was sent the following bug fix for the zoo timezone bug.  It changes
>the timezone field to a signed quantity.  I have not tested it. 
...
>This fix should be needed only if you are t hours east of GMT, such
>that 0 < t < 12, and if GETTZ is defined at compilation time.  Thanks
      ^^^^^^^^^^
>to Thomas P.S. Olesen <mcvax!dkuug!dde!tpo> for this.

A minor nit here:  the valid range of timezone offsets east of GMT is
minus twelve hours to plus thirteen hours, inclusive.  In UNIX and ZOO
terms, that's minus thirteen to plus twelve hours WEST of GMT.  
The timezone offsets minus twelve and plus twelve are not the same,
and neither are the minus thirteen and plus eleven timezones.

Why is there a minus thirteen zone?  There are quite a few politically-inspired
deviations in the International Date Line, especially around Siberia and
Pacific islands south of it.  Some countries didn't like the idea of having 
such a large time jump between parts of the same country.  I forget
exactly where, but there really is land in the minus thirteen zone.

The minus twelve and plus twelve zones would exist even if the International
Date Line were a straight line.  They ARE different.

				Gordon L. Burditt
				...!texbell!sneaky!gordon