You can import a shp file into JOSM.
Edit those polygons by splitting them into lines (I suppose you dont need to see 0x19 lines along the coast line).
Give those lines an appropriate tag (e.g. timezone=yes, name="GMT +2")
Save it as osm file, DO NOT upload it to OSM!
Run splitter/mkgmap on this osm file and make a transparent Garmin img;
in your line style you have to add a line to display timezone=yes.
Van: "greg crago" <gregcrago@gmail.com>
Aan: "Development list for mkgmap" <mkgmap-dev@lists.mkgmap.org.uk>
Verzonden: Donderdag 9 juni 2016 02:05:55
Onderwerp: Re: [mkgmap-dev] Has anyone added a USA TIMEZONE overlay ontop of their custom maps?
Great, how do I use a SHAPEFILE and assign it to a linetype 0x19 (a TIMEZONE linetype I have waiting)
Greg