[tz] Dealing with Pre-1970 Data

Lester Caine lester at lsces.co.uk
Mon Sep 2 15:25:14 UTC 2013

Paul Eggert wrote:
> Lester Caine wrote:
>> >MY proposal is that if the database returns LMT then it is a flag
>> >that we are working with 'pre standard time' dates
> OK, although that's a different timestamp than the one Guy Harris
> was talking about.  Guy Harris suggested a timestamp such that
> all clocks in the named region agree after that timestamp, and
> some disagree earlier.  For Europe/Paris that would be some timestamp
> in 1945, I expect; that information is not in the database now, and
> although a number could be deduced from the Shanks & Pottenger
> data it'd be almost certainly incorrect.  You want a timestamp
> such that time stamps before that date are LMT.  For Europe/Paris
> that's a timestamp in 1891, which*is*  deducible from the current
> database, and which is relatively reliable, at least for Paris.
> You should be able to implement the flag that you want,
> by consulting the current database.

And moving things forward it makes things logical? Prior to the adoption of a 
standard time, an individually calculated LMT is a more correct answer? The key 
fact here is simply when a standard time was adopted.

Since you bring up Paris ( and I'll admit to not looking in the database here 
... ) is French Railway time covered from 1891 to 1911 - INTERNAL station clocks 
were required to be set 5 minutes slow by law - so French. But I don't think we 
need a timezone per station :)

And it always tickles me that they 'set French Standard Time back 9minutes 21 
seconds' in 1911 rather than admitting to adopting GMT ...

Now that is interesting ... I knew about the railway time, but not that shipping 
time did not change for another six months ... these newspaper archives make 
interesting reading.

Lester Caine - G8HFL
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