Brian Inglis wrote:
On 01.07.1906 When completed construction Observatory Phu Lien, Indochina government decree dated 09.06.1906 (Official Gazette dated 18.06.1906 Indochina) fixed now legal for all countries of Indochina under the meridian passing through Phu Lien (104°17'17" east of Paris) from 0 hours on 01.07.1906.
Yes, thanks, I'm working my way through that web page. For that paragraph, I assume "east of Paris" means east of Paris Mean Time, which was legally 00:09:21 east of Greenwich, and since 104°17′17″ works out to 06:57:09.1333..., that would make Phù Liễn Mean Time legally 07:06:30.1333.... An alternate interpretation would be that it refers to François Arago's definition of the Paris Meridian; in that case Phù Liễn Mean Time would be the temporal equivalent of 2°20′14.03″ + 104°17′17″ east, which would be 07:06:29.33333.... Luckily both values round to 07:06:30, so we can use this rounded value under either interpretation. By the way, if Google Maps and <http://kml.inovmapping.com/Ph-Lin-Observatory> are to believed the observatory is a bit east of both values, at roughly 07:06:31; but perhaps they moved the observatory since 1906, and anyway the legal definition is close enough. I assume the abbreviation should be PLMT for Phù Liễn Mean Time.