library(mapproj)
# assumes that the time zone shape files have been downloaded
# from: http://openmap.bbn.com/data/shape/timezone/
tz <- read.shape('WRLDTZA')
plot(Map2poly(project.Map(tz,'bonne',param=45)))
plot(Map2poly(project.Map(tz,'bonne',param=45)),
col=rainbow(48)[tz$att.data$OFFSET])
plot(Map2poly(project.Map(tz,'albers',param=c(30,40))))
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