[tz] What is LMTZ?

Lester Caine lester at lsces.co.uk
Wed Sep 18 16:17:13 UTC 2013

Alan Barrett wrote:
>>> You often mention "LMTZ".  What does that term mean?
>> It was my attempt at separating the early LMT times everywhere, and the early
>> standardisations to an LMT based 'zone'
> What is an LMT based zone?  Zones are geographical areas, whereas LMT is
> associated with points.
>> Naively I assumed that would be an easier transition than it obviously
>> actually is? So we just move the switch-over point from 'location' based time
>> to timezones?
> Sorry, I am still too confused about your terminology to try answering that.

Hopefully we can agree that pre standardisation, people based their local time 
on 'midday' which is what what Local Mean Time is. and different locations have 
a different offset. Anything on the same longitude will be the same time.

When people started standardising they agreed on a Local Mean Time that applied 
across a bigger area. Now while towns may be on the same longitude their time 
offset would be different depending on the other locations in their group? I'm 
probably wrong but I am fairly sure that 'summer-time' or 'daylight saving is a 
20th century invention? So prior to that all time was 'mean time' and it just 
depended on which longitude was being used to set it. 1915 started messing 
things up with the first varying time rules?

Up until 1915 all we need to know is how the 'offset' from LMT was set when 
groups of locations agreed on a standard ... which is my 'LMTZ' data.

Lester Caine - G8HFL
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