Evan Siroky's Timezone Boundary Builder project has been generating open data about worldwide timezone boundaries for 10 years now! This talk will quickly review what the project is, how it started and ongoing development and maintenance challenges.

The Timezone Boundary Builder project is an open data project that produces a shapefile of the world's timezone boundaries that is derived from OpenStreetMap data. The project builds on top of the Timezone Database which includes the timekeeping data about timezones around the world, but only gives an approximate point-based location of each timezone. The released open data has been downloaded over 800,000 times and is used in software packages in all major software languages. Some of these packages are downloaded millions of times each week. Over the past 10 years, there have been 26 releases that have followed various releases to the Timezone Database project.

The project started out of a motivation to improve upon an existing open-data project in order to create more precise boundaries and also include territorial waters in the boundaries. Since then, a variety of improvements and quality assurance have been added over time. These include generating internal datasets of changes to release data, checking for overlapping boundaries, but in some cases allowing overlaps and most recently including derived datasets based on what timekeeping methods are in place after a certain point in time.

Over the years, various challenges have existed that make maintaining the project a challenge. The initial build-out of all timezone data took multiple months of work. The ever-changing data in OpenStreetMap requires attention to make sure that administrative boundaries have valid data. Various disagreements with members of the OpenStreetMap community on whether timezones should be included in OpenStreetMap at all also present challenges. And maintaining compatibility with a change to the Timezone Database that created 3 versions of the timezone data also added additional maintenance.

Given the complex topic and various challenges, the project has actually required sporadic maintenance while remaining very popular. Whenever the Timezone Database makes a new release, it typically takes a few days to create a new Timezone Boundary Builder release. This includes running a somewhat old node.js script to fetch data from OpenStreetMap and then translate it into GeoJSON and shapefile formats.

The project has enjoyed widespread adoption as a result of key timezone influencers. The maintainer of the Timezone Database, Paul Eggert included a note about the project, a former timezone boundary maintainer deprecated their project in favor of Timezone Boundary Builder and a popular Stakeoverflow answer was updated to note that Timezone Boundary Builder seemed to be the best option for timezone boundary data. Other than that, growth in usage of the project has been completely organic. I do have a way to accept GitHub Sponsors money, but the project has never been my day job.

Overall, the project has been an interesting way to learn about timezones and contribute something helpful to the open source and open data ecosystem.