[R-sig-Geo] Timezone boundaries (for adding to world map)?

[Martin Maechler]

Dear R - Mapping specialists,

for a prospective publication on using date/times etc in R,
we are looking for a way to draw a world map additionally with 
the "timezone stripes".

Thanks to Roger Bivand, it was easy to get to the world map:
I've used this
  http://spatial.nhh.no/R/etc/world_map_intro.html
and later also found
  https://stat.ethz.ch/pipermail/r-sig-geo/2006-March/000848.html

Note that I'm pretty much an ignorant of the diverse shapefile
and other GIS data formats,
[ Furthermore, I'd ideally get a solution (or an *.rda file) 
  that does not need the 'rgdal' package since that is very hard
  for me to get working on our departmental computer, notably the
  64-bit ones (problems in installing libgdal / proj.4 / ...).
  As it *is* working on some versions of R on some ubuntu servers,
  I could use it if needed. ]

Thank you very much in advance!

Martin Maechler, 
ETH Zurich