Sources & data

Postal codes

Japan Post, postal code data, UTF-8 one-record-per-line edition (20260831): download page.
Japan Post, romanized postal code data KEN_ALL_ROME (as of June 2025, updated about once a year): download page.
Terms: Japan Post states that it does not claim copyright on postal code data and that it may be freely distributed.
Processing: the two files are joined by postal code and Japanese town name. Special rows ("以下に掲載がない場合", "…の次に番地がくる場合", "…一円") are shown with English explanations. Japan Post truncates long romaji names; truncated city names are completed from the kana reading, and 851 towns not yet in the romanized edition are romanized by this site (marked *).

Cabinet Office, Government of Japan, "National Holidays" (syukujitsu_cao_20260925.csv), https://www8.cao.go.jp/chosei/shukujitsu/gaiyou.html. English names are translations by this site.

Spellings of 1,394 common English first names and surnames compiled by this site from common Japanese usage and checked against Cabinet Notice No. 2 of 1991, "Gairaigo no Hyoki" (Agency for Cultural Affairs). Other names are estimated by spelling rules and marked Estimated. No kanji (ateji) are offered because their meanings would be invented.

Era Name Act and the Cabinet Orders changing the era; Act on Calculation of Age; Civil Code Article 143; School Education Act Article 17.