Arrebol time zone database
Arrebol works out which time zone a place is in on the phone itself, without the network, from a database of time zone boundaries. That database is derived from timezone-boundary-builder, which is made from OpenStreetMap data, and is made available here, byte for byte the one inside the app, under the Open Database License (ODbL) 1.0.
光时在手机上离线判断一个地点属于哪个时区，用的是一份时区边界数据库。它由 timezone-boundary-builder（基于 OpenStreetMap 数据）生成，按开放数据库许可协议（ODbL 1.0）在此公开，与 App 内置的文件逐字节相同。
Versions
| Version | File | SHA-256 |
|---|---|---|
| 2026e | timezone21.bin (4.99 MB) build_zonedb.sh · SHA256SUMS | cc8a2c5579cb6139010c8ba47600b733670c1fb69b555ece321842e8a3e7c59a |
What it is
- Format: ZoneDetect database, format version 1, precision 21 (coordinates kept to about 20 m; the boundaries themselves are only as accurate as OpenStreetMap's), read with ZoneDetect's library. The file carries its own notice of its sources and this licence.
- Contents: every IANA time zone's boundaries, including the oceans (
Etc/GMT±N), from timezone-boundary-builder 2026e (timezones-with-oceans.shapefile.zip), and the country each zone belongs to, with country names from Natural Earth (public domain). - Only which zone a coordinate is in comes from here; each zone's offset on a given date comes from the IANA time zone database built into the phone.
Rebuilding it
sh build_zonedb.sh <work directory> <output directory> downloads the pinned inputs, checks each against its SHA-256, builds ZoneDetect's builder with shapelib 1.6.3 and writes timezone21.bin only if its SHA-256 is the one above. The builder's one sort is made stable and floating-point contraction is turned off, to take the compiler's and C++ library's choices out of the result. It is verified with Apple clang 21 on arm64; on any other toolchain the output is accepted only if its SHA-256 matches. The script lists every input, version and checksum.
Licence and attribution
The database is licensed under the Open Database License 1.0. It contains information from timezone-boundary-builder, which is made available under the ODbL, and is based on OpenStreetMap data, © OpenStreetMap contributors. Country names: Natural Earth, public domain. ZoneDetect is © Bertold Van den Bergh, BSD-3-Clause; shapelib is MIT (or LGPL-2.0-or-later). Arrebol's own code is not covered by the ODbL, and the app places no extra restrictions on this database.