Twilight & day-length geometry API

Returns solar declination, day length, and the sunrise/civil/nautical/astronomical twilight hour angles and band spans for a date and latitude (solar-depression geometry, returns null at polar day/night). Answers 'How long is twilight here?', 'Day length and twilight bands for this latitude?'.

Price$0.06per request

MethodPOST

Route/v1/space/twilight-times

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

spaceastronomytwilightcivil-twilightnautical-twilightastronomical-twilightday-lengthpositional-astronomy

API URLhttps://x402.hexl.dev/v1/space/twilight-times

Integration docs

Example request

{
  "date": "2024-06-21T00:00:00Z",
  "latitude": 40
}

Example response

{
  "date": "2024-06-21",
  "latitude": 40,
  "solarDeclinationDeg": 23.435723,
  "dayLengthHours": 15.01434,
  "sunriseSunsetHourAngleDeg": 112.60753,
  "civilTwilightHourAngleDeg": 120.82735,
  "nauticalTwilightHourAngleDeg": 131.26511,
  "astronomicalTwilightHourAngleDeg": 143.45547,
  "daylightPlusCivilHours": 16.11031,
  "daylightPlusNauticalHours": 17.50201,
  "daylightPlusAstronomicalHours": 19.1274,
  "civilTwilightDurationHours": 1.09598,
  "interpretation": "Day length ≈ 15.01434 h at latitude 40°."
}

Input schema

{
  "type": "object",
  "required": [
    "date",
    "latitude"
  ],
  "properties": {
    "date": {
      "type": "string",
      "description": "ISO 8601 date (UTC)",
      "examples": [
        "2024-06-21T00:00:00Z"
      ]
    },
    "latitude": {
      "type": "number",
      "description": "Observer latitude in degrees",
      "examples": [
        40
      ]
    }
  }
}

Output schema

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