lat/lon to time offset database

Dirkjan Ochtman dirkjan at
Thu Feb 3 19:19:42 UTC 2011

On Thu, Feb 3, 2011 at 19:54, Paul Koning <paul_koning at> wrote:
> So you need a database of zone boundaries -- which is likely to be fairly large.  Then you figure out which polygon in that database contains your current position.  From that, you have the zone rule that applies to this position.

Having spent a little time trying to extract country boundaries from
the openstreetmap data, (a) it's not very trivial to get right (and
this might be even harder to do correctly for timezone borders,
because they're less relevant to mapmakers), and (b) yes, it's
substantial amount of data.

Depending on if the embedded device is mobile or not, maybe you could
start by using a GeoIP-like service.



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