# Birthplace presets

The UI has seven existing Korean presets (unchanged canonical names, coordinates and Asia/Seoul zone), eight Chinese presets and eight Japanese presets. Names shown in the UI are localized; stored `place.name` remains the stable canonical name. Country order follows the UI language, with the other countries still available. Initial unsaved defaults are Seoul, Beijing and Tokyo. A language switch must not replace already entered or saved birthplace data.

New coordinates are representative populated-place points in WGS84, not precise hospital or address locations. Most are copied at the 0.001-degree precision displayed by GeoNames; Naha uses its record coordinates. No live geocoding or location upload is used. Users who know their exact birthplace can use the existing custom-place fields. Korean lunar calculation rules are unchanged by language or country.

## Coordinate sources and attribution

Checked 2026-10-18. Contains information from [GeoNames](https://www.geonames.org/), available under [Creative Commons Attribution 4.0](https://creativecommons.org/licenses/by/4.0/). Coordinate values are copied as displayed; city display names are localized for this app. GeoNames states that coordinates use WGS84 and supplies data without an accuracy warranty: [about](https://www.geonames.org/about.html), [terms](https://www.geonames.org/export/).

- Beijing, Shanghai, Guangzhou, Shenzhen, Chengdu, Chongqing, Wuhan, Xi'an: [GeoNames China cities](https://www.geonames.org/CN/largest-cities-in-china.html).
- Tokyo, Osaka, Kyoto, Yokohama, Nagoya, Sapporo, Fukuoka: [GeoNames Japan cities](https://www.geonames.org/JP/largest-cities-in-japan.html).
- Naha (26.21300, 127.67851), Asia/Tokyo: [GeoNames 1856035](https://www.geonames.org/1856035/naha.html).

All selected mainland Chinese cities use Asia/Shanghai; Japanese cities use Asia/Tokyo. The existing moment-timezone IANA data determines the historical UTC offset, including daylight saving transitions, from the birth date. These are zone identifiers, not fixed +08:00/+09:00 arithmetic. DST classification may remain null where the engine intentionally does not classify it; UTC offsets and instants remain available.

Historical offset fixtures use the [IANA tzdb Asia rules](https://data.iana.org/time-zones/tzdb/asia): China in 1991 and Japan in 1949 each have distinct winter and summer offsets. Tests assert both the numeric UTC offset and resulting UTC instant; they do not claim independent historical validation of all past local time practices.