Julian Date Converter API — Overview
- What it does: Converts between Gregorian dates, Julian Day Number (JDN), Julian Date (JD, includes fractional day), and Modified Julian Date (MJD); some implementations also convert to/from Unix timestamps and weekday indexes.
- Common endpoints / functions:
- GET /v1/julianday?date=YYYY-MM-DD[THH:MM:SS] → JD, JDN, MJD, unix
- POST /v1/convert { “julian”: 2460000.5 } → Gregorian date/time
- Utility endpoints: /to-unix, /from-unix, /weekday
- Auth: API key in header (commonly x-api-key) or Bearer token.
- Response: JSON with numeric JD (float) and derived fields; typical shape:
Code
{ “status”:“ok”, “data”: {"gregorian":"2026-02-04T12:34:56Z", "julian":2460000.02345, "jdn":2460000, "mjd":60000.02345, "unix":1675522496} }
Integration examples
JavaScript (fetch)
Code
const res = await fetch(’https://api.example.com/v1/julianday?date=2026-02-04T12:34:56Z’, { headers: { ‘x-api-key’: ‘YOURKEY’ } }); const json = await res.json(); console.log(json.data.julian);
cURL
Code
curl -H “x-api-key: YOURKEY” “https://api.example.com/v1/julianday?date=2026-02-04T00:00:00Z”
Python (requests)
Code
resp = requests.get(”https://api.example.com/v1/julianday”, params={“date”:“2026-02-04T12:34:56Z”},headers={"x-api-key":"YOUR_KEY"})print(resp.json()[“data”][“julian”])
Implementation notes / best practices
- Send times in ISO 8601 UTC to avoid timezone ambiguity; APIs may accept local times but results can differ.
- Check whether the API returns JD (starts at noon) or JDN (integer days) and whether fractional day uses UT or TT — astronomy applications sometimes require Terrestrial Time (TT) corrections.
- For high-precision needs include fractional seconds and confirm float precision (double recommended).
- Rate limits and API key security: store keys server-side, respect usage limits.
Libraries & tools
- Existing open-source options: APIVerve Julian Day Calculator (REST + SDKs), several language libraries (PHP, Rust crate, Python packages). Search GitHub or package registries (npm, PyPI, NuGet, crates.io) for language-specific clients.
If you want, I can generate ready-to-use client code for a specific language or an OpenAPI spec for this API.
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