Credits

astronomy-engine by Don Cross, MIT licence: the Sun's apparent longitude for the solar terms and the equation of time.
GeoNames (geonames.org), Creative Commons Attribution 4.0: the list of birthplaces with coordinates and time zones.
IANA time zone database, public domain, through your browser: historical clock offsets, including Korea's UTC+8:30 periods and summer time.
Fonts, all SIL Open Font License 1.1, served from this site as renamed subsets: Hahmlet by Hyper Type (headings), Gowun Dodum by Yanghee Ryu (text), Noto Serif KR by Google (Hanja) and Nanum Brush Script by NHN (the brush lettering). The licence files are served next to the fonts.
The twelve animals, the painted scenes and the seal are drawn in code for this site, in the spirit of Korean folk painting (minhwa) and older Korean art: the sun, moon and five peaks screen (일월오봉도) that stood behind the Joseon king's throne, the folk magpie and tiger (까치호랑이), the field mouse and watermelon from the insect and plant screen attributed to Shin Saimdang, the flying horse on the Silla saddle flap from Cheonmachong, and the moon rabbit.
Solar term times used to test the engine: Hong Kong Observatory, Date and Time of the 24 Solar Terms.
Reference charts used to test the engine: lunar-javascript by 6tail (MIT), used in testing only.