Standard Time Zones & Local Mean Time

Gwillim Law RLAW at
Sat May 7 14:55:57 UTC 2011

These are complex questions, hinging on subjective interpretations of the
terms involved, such as "general acceptance". The book "Greenwich Time and
Longitude", by Derek Howse, has a lot of information about standard time in
Great Britain. For example, he writes (pp. 114-15) that in 1858, a court
decided that legal time "must be understood as the mean time at the place
where" an event occurs, "and not Greenwich time, unless it be so expressed."
Prior to that, there had been "nothing on the statute book to define what
was the time for legal purposes" -- but at that date "98% of the public
clocks in Great Britain were set to GMT." On August 2, 1880, it finally
became law that "[w]henever any expression of time occurs in any Acts of
Parliament, deed, or other legal instrument, the time referred shall, unless
it is otherwise specifically stated, be held in the case of Great Britain to
be Greenwich mean time, and in the case of Ireland, Dublin mean time."
(Copyrighted material, quoted under fair use.) So perhaps that answers part
of your inquiry. You may have to hit the books in a good library if you want
more complete answers.

Gwillim Law

----- Original Message ----- 
From: "David Patte" <dpatte at>

> Does anyone have insight into the dates when standard timezones, based
> from Greenwich and at 15 degree intervals (as are still used in
> international waters) started coming into general acceptance or law? Am
> I correct to assume that the first place to use 'standard time' was
> Britain in 1847, but that the international acceptance of a 'world'
> timezone system based on GMT offsets only really started with Sir Andrew
> Fleming's proposals in 1879?
> Also, before that, when did 'mean time' as opposed to 'solar time' start
> coming into general acceptance? I read that it was when accurate
> mechanical clocks started becoming available in the early 1800s. Anyone
> have an approximate date for first adoption of mean time by a city?

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