timezones-api VS timezone-boundary-builder

I wrote a tutorial on SpatiaLite here: https://datasette.io/tutorials/spatialite - "Building a location to time zone API with SpatiaLite"

It shows how to use SpatiaLite + Datasette to build an API that can tell you what timezone a latitude/longitude point is in, using data derived from OpenStreetMap via https://github.com/evansiroky/timezone-boundary-builder

Here's a demo: https://timezones.datasette.io/timezones/by_point?longitude=... - add ".json" to the URL for the JSON output.

It had been quite a while since a major release, but then SpatiaLite 5.0 came out a couple of months ago with some very significant new features - the K-Nearest-Neighbor stuff is particularly interesting. https://www.gaia-gis.it/fossil/libspatialite/wiki?name=5.0.0...

I've built a few fun demos using SpatiaLite and Datasette. Here's an API that tells you the timezone for a latitude longitude point:

https://timezones-api.datasette.io/timezones/by_point?longit... - implementation here: https://github.com/simonw/timezones-api

And here's the same thing for which US county a point is within: https://us-counties.datasette.io/counties/county_for_latitud... - implementation here: https://github.com/simonw/us-counties-datasette

I've also built an experimental Datasette plugin that lets you draw a shape on a Leaflet map to generate a GeoJSON polygon, then uses SpatiaLite to show you geometries that are contained by that drawn polygon. I wrote about that here: https://simonwillison.net/2021/Jan/24/drawing-shapes-spatial...

They don't really bother me. They aren't AI spam, and some folks may enjoy them. It's pretty easy to not click on a link, for me.

TZ are a fun project. I found that it's difficult to translate a long/lat into a TZ ID, so I wrote this[0].

Works a charm. It's based on the Timezone Boundary Builder[1].

[0] https://github.com/LittleGreenViper/LGV_TZ_Lookup

[1] https://github.com/evansiroky/timezone-boundary-builder

I wrote a tutorial on SpatiaLite here: https://datasette.io/tutorials/spatialite - "Building a location to time zone API with SpatiaLite"

It shows how to use SpatiaLite + Datasette to build an API that can tell you what timezone a latitude/longitude point is in, using data derived from OpenStreetMap via https://github.com/evansiroky/timezone-boundary-builder

Here's a demo: https://timezones.datasette.io/timezones/by_point?longitude=... - add ".json" to the URL for the JSON output.

I have never had an opportunity to deploy this tool, but here's a program for generating a TZ shapefile from OpenStreetMap data:

https://github.com/evansiroky/timezone-boundary-builder

In principle a calendar program could use its output to perform GIS lookups of locations then use the tzinfo DB to get the correct timezone at the given location and specified time.

You could ask google. Amazon or Microsoft probably offer similar APIs. Or you can do it yourself. It's a very complicated topic, though.

There is a separate timezone boundary builder which maps geography to timezones using a shapefile, and the shapefile is >35MB uncompressed. By comparison the latest tzdata is 1.2M uncompressed.