[tz] Etc/GMT timezone offsets are inverted

[Paul Eggert]

Pedro A. López-Valencia wrote:
> I just noticed that all GMT+- timezones are inverted

There is a comment about this in the "etcetera" file:

# Be consistent with POSIX TZ settings in the Zone names,
# even though this is the opposite of what many people expect.
# POSIX has positive signs west of Greenwich, but many people expect
# positive signs east of Greenwich.  For example, TZ='Etc/GMT+4' uses
# the abbreviation "-04" and corresponds to 4 hours behind UT
# (i.e. west of Greenwich) even though many people would expect it to
# mean 4 hours ahead of UT (i.e. east of Greenwich).