[tz] Recent conversions of zones to aliases
guy at alum.mit.edu
Fri Oct 3 20:37:35 UTC 2014
On Oct 3, 2014, at 12:58 PM, Lester Caine <lester at lsces.co.uk> wrote:
> On 03/10/14 20:38, Guy Harris wrote:
>> 1) have a database to map locations to tzids;
> This is what geonames currently provides, but using the 'full' TSID list
> from TZ currently.
So presumably by "location" you mean "something with an entry in the GeoNames database":
rather than "a longitude+latitude".
In either case, for any given location, the tzid and longitude+latitude can be determined, with the help of the appropriate databases.
> What is missing is the gap between what is valid data on TZ and the
> actual location based history.
> For example when Oxford switched from Oxford time to Europe/London and
> in parallel when railway time was used at the station. Basically how to
> add this historic data to the time offset system.
So how was "Oxford time" defined? Was there a specified offset, or was it just, for example, mean solar time at some location in Oxford, or mean time wherever you happened to be in Oxford?
Note that the GeoNames site says, "The GeoNames geographical database covers all countries and contains over eight million placenames that are available for download free of charge.", so if every location in the GeoNames database has a separate offset, that's unlikely ever to be in the tz database.
The tz database is not, and should not ever be, the place to go for information about solar-time-based local time. A case *might* be made for local times that aren't solar-time-based but that weren't standardized in the "standard time" sense, if any such local times existed.
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