The very first response, from Jeff Newmiller, included a link http://efele.net/maps/tz/world/ which says it has offers a shapefile of timezones of the world.
An outline of a solution, then it to download the shapefile load it into R input your lat/long data into R use the over() function in the sp package Of course there are many details amongst those steps; I would suggest r-sig-geo would be the place for help with those details. It remains to be seen whether the way in which the timezones are identified in that shapefile is compatible with how timezones are identified in R POSIXt classes (R uses the OS for this). Daylight savings time information is, I believe, provided by the OS for at least some time zones, but I don't know if its provided for all of them. -Don -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 9/23/13 7:05 AM, "carlisle thacker" <carlisle.thac...@gmail.com> wrote: >Gabor, > >Thanks for your tip about zone.tab. It provides country codes and lat/lon >of the zone's principal location, which while useful is not exactly what I >need. I would like to know the coordinates of time zone boundaries. >Better still would be a function, which returns the name of the time zone >in which given lat/lon is situated. > >For example, in which time zone is 22N,166W? And at what times of year >might daylight savings time be in effect? > >Regards, > >Carlisle > > >On Sat, Sep 21, 2013 at 3:17 AM, Gabor Grothendieck ><ggrothendi...@gmail.com >> wrote: > >> On Fri, Sep 20, 2013 at 4:31 PM, carlisle thacker >> <carlisle.thac...@gmail.com> wrote: >> > I was looking for something like shown on the map: >> > >> >>http://upload.wikimedia.org/wikipedia/commons/8/88/World_Time_Zones_Map.p >>ng >> > >> > 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. >> >> The zone.tab file has this information. See the Examples section at >> the end of ?Sys.timezone for info on its whereabouts. >> > > [[alternative HTML version deleted]] > >______________________________________________ >R-help@r-project.org mailing list >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide >http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
