I was looking for something like shown on the map:
http://upload.wikimedia.org/wikipedia/commons/8/88/World_Time_Zones_Map.png

Information about local daylight savings times would also help.

The data are from ships, supposedly in local time, but no time-zone info is
given.  A function that would return time zone and whether or not daylight
savings time applies at given date would would help.  I'm trying to track
down more information about the data and whether they can be referenced to
UTC.


On Fri, Sep 20, 2013 at 2:18 PM, David Winsemius <dwinsemius@comcast.net>wrote:

>
> On Sep 20, 2013, at 8:02 AM, carlisle thacker wrote:
>
>  I have data that provide longitude, latitude, and local date and time but
>> no information about the corresponding time zone.  How to identify the
>> time
>> zone so they can be converted to a common date/time?
>>
>
> Perhaps as an approximation you could divide the longitude by 360/24,
> truncate and subtract to get an estimated GMT. It really depends on your
> purposes, the encoding of "local time", need for accuracy, and perhaps
> further details regarding the data collection methods, none of which you
> have provided.
>
> --
>
> David Winsemius, MD
> Alameda, CA, USA
>
>

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