A suggestion for improving the accuracy of LMT of Asia/Tokyo

Alan Barrett apb at cequrux.com
Thu Jan 20 18:18:50 UTC 2011

On Wed, 12 Jan 2011, Fumiyuki Shimizu wrote:
> With regards to the current LMT of Asia/Tokyo, there are two problems.
> 1. It is based on 'Tokyo Datum' using Bessel ellipsoid of which
>    equatorial radius, and flattening are less accurate than GRS80.
> 2. Location of origin point used by 'Rika Nenpyou (until 2009)' was
>    not commonly used for geodetic reference system in Japan.

That line in the rules ...

>  # Zone NAME            GMTOFF  RULES   FORMAT  [UNTIL]
>  Zone   Asia/Tokyo      9:18:59 -       LMT     1887 Dec 31 15:00u

... is talking about the local mean time as it was before 31 Dec 1887;
it's not the "current" LMT.

The oldest reference in your message seemed to be for the year 1892.  Do
you have information about the official time in Tokyo before or during
the year 1887?

--apb (Alan Barrett)

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