R help - Sep 2013 - time zones from longitude, latitude, and date

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?

Thanks,

Carlisle

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If you make no further assumptions then this question is not solvable. For
example we use standard time in our data collection systems even though legal
time here applies daylight savings offset in the summer. In some cases I have
seen data collected from sites in multiple time zones recorded in one data base
with a single time zone.
Even if you do assume local legal time applies in all cases, the boundaries of
the time zones have changed over time. There exist time zone maps (e.g.
http://efele.net/maps/tz/world/) that you could assume apply but I am not aware
of any in CRAN. Someone on r-sig-geo might be able to help.
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carlisle thacker <carlisle.thacker at gmail.com>
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?
>
>Thanks,
>
>Carlisle
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
>R-help at r-project.org mailing list
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>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

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

carlisle thacker <carlisle.thacker <at> gmail.com> writes:


> 
> 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?
> 
> Thanks,
> 
> Carlisle
> 
> 	[[alternative HTML version deleted]]
> 
> 


Hi list,



maybe I didn't read the post carefully enough, but what about using the 
GNtimezone in Barry Rowlinson's "geonames" package ?



Olivier