How to look up historical time zones by date and location

[Denis McMahon]

On Mon, 18 Aug 2014 12:55:59 +0800, luofeiyu wrote:

> http://www.thefreedictionary.com/time+zone
> 
> time zone Any of the 24 divisions of the Earth's surface used to
> determine the local time for any given locality.
> Each zone is roughly 15° of longitude in width, with local variations
> for economic and political convenience.
> Local time is one hour ahead for each time zone as one travels east and
> one hour behind for each time zone as one travels west.
> 
> Urumqi  's localtime is beijin time ,it is decided  by law .
> Urumqi  's timezone is east 6 ,it is decided by geography.
> 
> There is only one localtime in all over the chian,beijin time,but there
> are 5  timezone time in china .
> 
> you are totally wrong ,not me .

The Oxford Dictionaries ( http://www.oxforddictionaries.com/definition/
english/zone?q=timezone#zone__8 ) definition of zone includes:

"(also time zone) A range of longitudes where a common standard time is 
used."

freedictionary has a very broad definition of time zone and is probably 
slightly less authoritative on the definition of English words than the 
Oxford University Press.

Most timezones may even be roughly 15 degrees in longitude in width, but 
this is not binding, and it is not unusual to find other widths applied.

In the case of China, the Chinese government has determined that the 
whole country operates on Beijing Time, so the time zone *FOR ALL OF 
CHINA* is that of Beijing.

The astronomical time[1] in Urumqi may not match the time zone, however 
the time zone is Beijing Time.

[1] I consider astronomical noon for any point as being when the sun is 
at zenith, ie overhead of the longitude of the point[2].

[2] Yes, I realise this means that it's always noon, and midnight, and 
everything else at the poles, I just have to live with that.

-- 
Denis McMahon, denismfmcmahon at gmail.com