[tz] Support for Etc/GMT -style zones ids with partial hours

[Steve Allen]

On Wed 2020-10-21T18:12:13+0100 Neil Fuller via tz hath writ:
> Would there be any support in this community for adding new Etc/GMT[-+]
> zone identifiers but with partial hours? e.g. something like "Etc/GMT-5:30"

If this happens then at the same time I would like to see the full-hour
zones extended to support pre-1925 astronomical calendars which are
still in use at observatories.  In particular
Etc/GMT+20
has been the basis of the calendar at Lick Observatory for 130+ years.

--
Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
1156 High Street               Voice: +1 831 459 3046         Lng -122.06015
Santa Cruz, CA 95064           https://www.ucolick.org/~sla/  Hgt +250 m