Japan Business Tools

Return the date that is N business days after (or before, if N is negative) the given date. The start date itself is not counted; e.g. 1 business day after a Friday is the next Monday unless it is a holiday. / n営業日後（nが負なら前）の日付。起算日は数えない。

If the date is a business day, return it as is; otherwise move to the next ("next") or previous ("previous") business day. Useful for payment due dates that fall on holidays. / 営業日ならその日、休みなら次（next）または前（previous）の営業日。支払日が休みのときなどに使う。

Check whether a date is a business day in Japan, and if not, why (weekend, holiday name, bank closure, or a custom closed day). `reason` is Japanese text; `reason_code` is one of weekend, holiday, bank_closure, extra_holiday (null on business days). flags: `estimated`/`unverified` when the year's holidays are an estimate. / その日が営業日かどうかと、休みの理由（土日・祝日の名前・銀行の休業日・指定された休日）。reason_code は weekend・holiday・bank_closure・extra_holiday。

Count business days from start to end, inclusive of both ends. Returns 0 if start is after end. The period can be up to 3,660 days (about 10 years). / start から end までの営業日の数（両端を含む）。start が end より後なら 0。期間は3,660日（約10年）まで。

Convert a Japanese era date to YYYY-MM-DD. Accepts 令和8年10月7日, 令和元年5月1日, R8.10.7, H31/4/30, Reiwa 8.10.7, kanji numerals (昭和六十四年一月七日), a trailing weekday such as （水） or 水曜日, and full-width characters. `input_era`/`input_era_year` echo the input; `actual` is the correct era for that date. If the date is outside the input era (e.g. 平成31年5月1日, written after the era changed), it is still converted by counting years, `within_era` is false and flags has `outside_era`. If a weekday was given and does not match, `weekday_matches` is false and flags has `weekday_mismatch`. / 和暦の日付を西暦にする。元号の範囲の外（平成31年5月1日など）も年を数えて変換し、within_era が false・flags に outside_era。曜日が合わなければ weekday_mismatch。

Return the last business day of the given month. / その月の最終営業日。

List all Japanese national holidays and substitute holidays for a year, based on the National Holidays Act and verified against the Cabinet Office CSV. Each holiday has `name` (descriptive) and `official_name` (as written by the Cabinet Office). / その年の国民の祝日・休日（振替休日・国民の休日を含む）の一覧。name は内容がわかる名前、official_name は内閣府の表記。

Look up a 13-digit Japanese corporate number (法人番号) in the National Tax Agency's monthly bulk data: name, furigana, English name, kind, registered address and postal code, assignment date, and closure (date, cause, successor) if the registry record was closed. The check digit (first digit) is verified first; a wrong check digit is reported as an input error. flags: `closed` (the registry record is closed — tell the user), `excluded_from_search`, `not_found`. This is not the invoice (qualified invoice issuer) registry. / 法人番号（13桁）から、名前・フリガナ・英語の名前・法人の種類・所在地・郵便番号・指定の日・閉鎖の日と事由・承継先を返す。国税庁の全件データ（月1回）。先頭の1桁（チェックデジット）を確かめ、合わなければ入力の誤りとして返す。インボイス（適格請求書発行事業者）の登録の確認ではない。

Look up the address (prefecture, city, town) for a 7-digit Japanese postal code, from Japan Post data. Accepts forms like 1000001, 100-0001 or 〒100-0001. One code can cover several towns; all are returned. `town_detail` holds the parenthesized part as written by Japan Post (e.g. chome ranges or building floors). If the code is a business-specific code (大口事業所個別番号) or a PO box code, the business is returned in `offices`. / 郵便番号から住所（都道府県・市区町村・町域）。日本郵便のデータ。1つの郵便番号に町域が複数あれば、すべて返す。事業所の個別郵便番号なら、事業所名と所在地を offices に返す。

Split a Japanese address into prefecture, city, town and the rest (block numbers, building), matching Japan Post's address data, and return candidate postal codes. Absorbs full/half-width, spacing, kanji vs. arabic numerals, ヶ/ケ and omitted county names; fills in the prefecture when the city is unique. Does NOT verify block/house numbers and has no coordinates. `level` tells how far the match went: 0 = nothing matched, 1 = prefecture only (see `city_candidates` if the city name is ambiguous), 2 = city matched but not the town (`postal_codes` are city-wide candidates), 3 = town matched. `address` and `municipality_code` are null below level 2. flags: `partial` (level below 3), `ambiguous` (several city or postal code candidates — ask the user or show all). / 住所を都道府県・市区町村・町域・残り（番地・建物名など）に分け、郵便番号の候補を返す（日本郵便のデータにあてはめる）。番地が実在するかの確認と緯度・経度はない。level：0＝わからない、1＝都道府県まで、2＝市区町村まで（町域はわからない）、3＝町域まで。

Find Japanese corporations whose name starts with the given text (prefix match), in the National Tax Agency's monthly bulk data. Legal-form words such as 株式会社 or 一般社団法人 are ignored at either end, and full/half-width and spaces are normalized. Matching in the middle of a name and furigana search are not supported. flags: `truncated`, `exact_match_only` (too many names start with the input; only exact matches returned), `not_found`. Returns up to 100 matches (`total`, `returned`, `truncated`) with corporate number, name, prefecture, city and `is_closed` (registry record closed); use lookup_corporate_number for details. Corporations marked as excluded from search on the NTA site are not included. / 名前の先頭から合う法人を探す（前方一致）。株式会社などの言葉は前後どちらにあっても無視し、全角・半角や空白の違いも吸収する。名前の途中からの検索とフリガナの検索はできない。最大100件。詳しい情報は lookup_corporate_number で。国税庁のサイトで検索対象除外の法人は入っていない。

Find Japanese postal codes by prefecture, city and (optionally) part of the town name, from Japan Post data. The city must be the full municipality name (e.g. 札幌市中央区, 新宿区); the county name may be omitted. With `office_name`, searches business-specific codes (大口事業所個別番号) of businesses in that city by name instead. Returns up to 100 matches. / 都道府県・市区町村・町域（部分一致、任意）から郵便番号を探す。市区町村は正式な名前で（郡名は省いてよい）。office_name を指定すると、その市区町村の事業所の個別郵便番号を事業所名（部分一致）で探す。

Convert a Gregorian date (YYYY-MM-DD) to the Japanese era calendar, e.g. 2026-10-07 → 令和8年10月7日 (wareki_short R8.10.07, zero-padded). Year 1 is written 元年. Supported from 1873-01-01 (the Gregorian calendar was adopted on 明治6年1月1日). Eras: 令和 (R) from 2019-05-01, 平成 (H) from 1989-01-08, 昭和 (S) from 1926-12-25, 大正 (T) from 1912-07-30, 明治 (M) from 1868-01-25. flags: `assumes_current_era` for dates after today (the era might change). / 西暦の日付を和暦にする。1年目は「元年」。明治6年（1873年）1月1日から。今日より後の日付には assumes_current_era。