On Sat 2020-11-07T15:21:43+0000 Michael H Deckers via tz hath writ:
So the switch in the local civil time for Belize on 1912-04-01 was from T - 05:52:42.33 h to T - 06 h, where T is the realization of UT by the timing observatory for Belize at the time. And this is the fact that tzdb had to represent (possibly up to rounding). That T must have been off from UT by several seconds is also suggested by the telegraphy data of Milne, who reports that the Belize Court House clock was about UT - 05:52:47 h around 1899.)
The longitude of Belize in the 1787 map by William Faden had the coastline much farther west at longitude greater than 89 degrees. https://www.loc.gov/item/86692592/ The Roschshoof map from 1867 is closer to modern longitudes. https://www.loc.gov/resource/g4820.lh000157/ Ships with significant draft cannot approach Belize City, and it is plausible that the conventional time for Belize was set for a longitude off shore where the ships could anchor as contrasted with any point on the land itself. The 1912 record for the change in the time should be believed whether or not it corresponds to a longitude of a known place. -- Steve Allen <sla@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