![]() ![]() It spans nearly 30 degrees longitude (68☇E to 97☂5E). India is a large country that stretches almost 3000 kilometers (1864 miles) from west to east. However, the UTC+5:30 offset has been used as the local standard time in India since 1906. If you zoom in, you can see the effect of the extreme quantization but the map looks good from far away. The country has officially observed India Standard Time (IST) since 1947. The -p “Name” port keeps the Name of each time zone section in the topoJSON file so that I can use it in tooltips. ![]() Topojson -o timezones-topo2.json -p “Name” -q 1e2 timezones.json I first used ogr2ogr to turn the timezone.kml file into GeoJSON and then I used the following TopoJSON command to simplify and quantize the file into a small topoJSON file: As can be seen on the map above, some time-zones seem to defy logic and were mostly drawn by national or regional governments to make commerce and administration easier. TopoJSON actually supports GeoJSON, TopoJSON, ESRI shapefile, CSV, and TSV files for conversion and the installation is dead simple because it runs on Node.JS and can be installed using NPM. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time. TopoJSON is pretty awesome because it not only makes GeoJSON files much smaller but it also gives you many options around simplification, quantization, and conversion. A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. I found a KML file of time zones here and decided to quickly put together a D3.js time zone world map using TopoJSON. After some browsing, I did find a OpenLayers and Gmaps time zone map implementation but it does not use GeoJSON. In each geographic region within a time zone, people use the same time. Each section observes a uniform standard time to keep track of the day and night cycle and also for legal, social and commercial purposes. I was doing some API work with time zones recently and was surprised not to find a D3 time zone map implementation. A time zone is one of 24 spherical lunes with equal width-each assigned with one of the 24 hours.
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