Julian Date <-> Gregorian API

Converts between an astronomical Julian Date (and Modified JD) and a Gregorian instant in both directions using exact JDN arithmetic. Answers 'What is the Julian Date for J2000.0?', 'Convert JD 2451545.0 to a calendar date.'.

Price$0.04per request

MethodPOST

Route/v1/datetime/julian-date

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

datetimejulian-datejdnmodified-julianastronomygregorianconvertepoch

API URLhttps://x402.hexl.dev/v1/datetime/julian-date

Integration docs

Example request

{
  "op": "to-julian",
  "date": "2000-01-01T12:00:00Z"
}

Example response

{
  "op": "to-julian",
  "date": "2000-01-01T12:00:00.000Z",
  "julianDayNumber": 2451545,
  "julianDate": 2451545,
  "modifiedJulianDate": 51544.5,
  "interpretation": "2000-01-01T12:00:00.000Z = JD 2451545 (JDN 2451545, MJD 51544.5)."
}

Input schema

{
  "type": "object",
  "required": [
    "op"
  ],
  "properties": {
    "op": {
      "type": "string",
      "enum": [
        "to-julian",
        "from-julian"
      ],
      "examples": [
        "to-julian"
      ]
    },
    "date": {
      "type": "string",
      "examples": [
        "2000-01-01T12:00:00Z"
      ]
    },
    "julianDay": {
      "type": "number",
      "examples": [
        2451545
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}