---
title: "Convert a Japanese era date (wareki) to a Gregorian date / 和暦から西暦"
method: GET
path: "/v1/japanese-era/from-era"
---

# Convert a Japanese era date (wareki) to a Gregorian date / 和暦から西暦

`GET /v1/japanese-era/from-era`

## Request

- Base URL: `https://biz.ossalt.jp`
- URL: `https://biz.ossalt.jp/v1/japanese-era/from-era`
- Auth: none declared

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。

## Query parameters

- `wareki` string, required: Japanese era date, e.g. 令和8年10月7日 or R8.10.7 / 和暦の日付

## Response `200`

OK

- Answer
  - `result` object, required: The answer / 結果
  - `source` object, required: Source and verification / 出典と照合の状況
  - `as_of` string, required: Reference date in Japan time (YYYY-MM-DD) / 基準日（日本時間）
  - `notes` string[], required: Assumptions such as estimated values / 前提（見込みの値など）
  - `flags` string[], required: `flags` holds machine-readable codes: `estimated` (a value is an estimate, e.g. a future equinox day — tell the user), `unverified` (year not yet checked against Cabinet Office data — tell the user), `assumes_current_era` (a future date written in the current era — tell the user), `outside_era` (the era date given is outside that era), `weekday_mismatch`, `closed` (the company's registry record is closed — tell the user), `excluded_from_search`, `truncated`, `not_found`, `exact_match_only`, `partial`, `ambiguous`, `city_not_found`, `ambiguous_city`.

## Other responses

- `400`: Invalid parameters / 入力の誤り
- `429`: Too many requests / 呼び出しが多すぎます
- `503`: Data unavailable / データを読めない

---

[API](https://skmtc.dev/ossalt/apis/japan-business-tools.md) · [All operations](https://skmtc.dev/ossalt/apis/japan-business-tools/llms.txt) · [OpenAPI document](https://skmtc.dev/ossalt/apis/japan-business-tools/revisions/8bb72a25e175?raw)