On Thu 2022-07-28T17:01:31-0700 Paul Eggert hath writ:
Thanks. Sorry to have induced you to go to all that work in digging up historical measurements of the Paris Meridian, as the current datum doesn't depend on the exact value. It's simpler, I think, to remove that longitude from the comments as that will save us the trouble of picking and citing a longitude. Done in the attached patch.
Rounding to 0.01 s is the right thing to do. In the 1920s, the first decade of operation, the BIH only attempted to specify time differences to 0.01 s between European observatories with the best clocks and equipment. The story of time in Indochina must still be richer than is in tzdata. One of the early radio broadcasts monitored as part of the work of the BIH was the station in Saigon. Time signals from Saigon began for the first World Operation in Longitude during 1926 October/November. See the picture in the New York Times article from 1925 https://www.nytimes.com/1925/09/06/archives/scientists-to-test-drift-of-cont... These were rhythmic signals which provided Greenwich Mean Time, so time-zone-like time was available to any site with a radio receiver. Those signals continued routinely until 1941-12-08 when the BIH described (my translation) After 1941 December 8, in effect, the station, only having one emitter, found it necessary, on many dates, to sacrifice the time signals for exigencies of traffic. -- 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