More info here:
http://www.nmm.ac.uk/explore/astronomy-and-time/time-facts/spring-forward-100-years-of-british-summer-time

In particular see "Permanent summer, 196871", which is visible in Ruby:

>> require 'time'
=> true
>> Time.parse("1 jan 1968")
=> Mon Jan 01 00:00:00 +0000 1968
>> Time.parse("1 jan 1969")
=> Wed Jan 01 00:00:00 +0100 1969
>> Time.parse("1 jan 1970")
=> Thu Jan 01 00:00:00 +0100 1970
>> Time.parse("1 jan 1971")
=> Fri Jan 01 00:00:00 +0100 1971
>> Time.parse("1 jan 1972")
=> Sat Jan 01 00:00:00 +0000 1972

So I'm pretty sure that the underlying tzinfo library is giving out true 
information about what timezone was being used at the time.

> This is a trace from Brian Lopez
> 
> brianmario@Brians-iMac mysql2.git (master): ruby -e 'p
> Time.local(2010); p Time.local(1940); p Time.local(1807)'
> Fri Jan 01 00:00:00 -0800 2010
> Mon Jan 01 00:00:00 -0800 1940
> Thu Jan 01 00:00:00 -0800 1807

Sure, well I guess that's West Coast USA. The USA will have had its own 
rules for this sort of thing.

> This one is from José Valim
> 
> jose:~/Work[ree-1.8.7-2010.02][master]$ ruby -e 'p Time.local(2010); p
> Time.local(1940); p Time.local(1807)'
> Fri Jan 01 00:00:00 -0200 2010
> Mon Jan 01 00:00:00 -0300 1940
> Thu Jan 01 00:00:00 -0306 1807

Argentina perhaps? Again, a different set of politics and rules.

> Have you noticed also that for 1807 I get -0014 and -0015?

I get something similar:

>> Time.parse("1 jan 1847")
=> Fri Jan 01 00:00:00 -0001 1847
>> Time.parse("1 jan 1848")
=> Sat Jan 01 00:00:00 +0000 1848
>> Time.local("1847").utc_offset
=> -75
>> Time.local("1848").utc_offset
=> 0

Sorry, I can't explain that one. I've heard of half-hour time zones and 
even quarter-hour ones, but not a minute and a quarter :-)

B.
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