The IANA timezone database[0] contains some real gems in the comments. A lot of research has gone into making it as accurate as possible. For instance, at the

The IANA timezone database[0] contains some real gems in the comments. A lot of research has gone into making it as accurate as possible. For instance, at the top of the UK entries in the "europe" file, you get this: # From Peter Ilieve (1994-07-06): # # On 17 Jan 1994 the Independent, a UK quality newspaper, had a piece about # historical vistas along the Thames in west London. There was a photo # and a sketch map showing some of the sightlines involved. One paragraph # of the text said: # # 'An old stone obelisk marking a forgotten terrestrial meridian stands # beside the river at Kew. In the 18th century, before time and longitude # was standardised by the Royal Observatory in Greenwich, scholars observed # this stone and the movement of stars from Kew Observatory nearby. They # made their calculations and set the time for the Horse Guards and Parliament, # but now the stone is obscured by scrubwood and can only be seen by walking # along the towpath within a few yards of it.' # # I have a one inch to one mile map of London and my estimate of the stone's # position is 51 degrees 28' 30" N, 0 degrees 18' 45" W. The longitude should # be within about +-2". The Ordnance Survey grid reference is TQ172761. # # [This yields GMTOFF = -0:01:15 for London LMT in the 18th century.] Or in the "northamerica" file: # From Arthur David Olson (2011-02-09): # I just spoke by phone with a staff member at the Metlakatla Indian # Community office (using contact information available at # http://www.commerce.state.ak.us/dca/commdb/CIS.cfm?Comm_Boro_name=Metlakatla # It's shortly after 1:00 here on the east coast of the United States; # the staffer said it was shortly after 10:00 there. When I asked whether # that meant they were on Pacific time, they said no - they were on their # own time. I asked about daylight saving; they said it wasn't used. I # did not inquire about practices in the past. And for furthere errata, I will mention the artist William Kentridge, whose video installation "The Refusal of Time"[1] was one of the cooler pieces I've seen in the last few years. [0]: http://www.iana.org/time-zones http://www.iana.org/time-zones [1]: https://www.youtube.com/watch?v=uaPnBorIMmc https://www.youtube.com/watch?v=uaPnBorIMmc (YouTube doesn't really do it justice, but if you like art and you ever get the chance to see it, I highly recommend taking the time)