[tz] Dealing with Pre-1970 Data
lester at lsces.co.uk
Fri Aug 30 22:03:52 UTC 2013
Guy Harris wrote:
> not create any new tzdb zones if the only reason for the new zone is "before standard time was established, these two locations had different LMT".
I have no problem with that.
I see no reason for LMT being returned when looking for a TZ offset, but there
is well documented TZ data prior to 1970 which should be retained and returned.
The various API's simply need to switch to an alternative when a date is prior
to 'known timezone time', but we are probably going to argue if that date is
1884 or something later? Certainly some of the links provided have shown the
politics involved so nothing has changed there :)
> Historical rules*subsequent to* time zone establishment, however, are arguably worth keeping and perhaps even updating, albeit perhaps with a disclaimer saying we can't guarantee historical accuracy and/or that they are subject to change due to additional historical information being found.
There are notes as to the accuracy of some data and that is all one can do. It's
that material that we were fighting to maintain the independence of recently?
Personally I can see a future linkup here with the historic mapping fork on
openstreetmap. The various changes over time to both the timezone bands, and the
daylight saving areas need to be documented and linked to the chronology so that
one can track the changes at any location. This is where I would expect LMT to
be generated since location is accurately defined, and while the Greenwich
Meridian only came into being in 1884, there is perfect sense in 'mapping' times
prior to that based on the offset of midday from it for earlier times? This is
also an historically correct fact once clocks were being used and synchronising
that with the latter zero of UTC is just logical? Now WHEN was the sun dial
Lester Caine - G8HFL
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