Almanac API

Retrieve a full-year solar almanac for any location.

GET /solar/almanac

Returns solstices, equinoxes, solar noon drift, and day-length data for the requested year.

Parameters

Parameter	Required	Type	Description
`lat`	✅	`float`	Latitude
`lng`	✅	`float`	Longitude
`year`	No	`int`	Year (default: current year)

Example

curl "http://localhost:8090/solar/almanac?lat=51.5074&lng=-0.1278&year=2026"

Response

{
  "latitude": 51.5074,
  "longitude": -0.1278,
  "year": 2026,
  "solstices": {
    "summer": {"utc": "2026-06-21T10:24:00Z", "solar_noon": "13:02", "day_length_h": 16.7},
    "winter": {"utc": "2026-12-21T20:50:00Z", "solar_noon": "11:58", "day_length_h": 7.8}
  },
  "equinoxes": {
    "spring": {"utc": "2026-03-20T14:45:00Z", "solar_noon": "12:04", "day_length_h": 12.1},
    "autumn": {"utc": "2026-09-22T20:05:00Z", "solar_noon": "12:09", "day_length_h": 12.1}
  },
  "solar_noon_extremes": {
    "earliest_utc": {"date": "2026-11-03", "time": "11:44"},
    "latest_utc": {"date": "2026-02-11", "time": "12:14"}
  },
  "civil_solar_offset_annual_mean_min": -10.3,
  "days": [
    {
      "date": "2026-01-01",
      "sunrise_utc": "08:06",
      "solar_noon_utc": "12:02",
      "sunset_utc": "15:58",
      "day_length_h": 7.87,
      "equation_of_time_min": -3.2
    }
  ]
}

The days array contains one entry per day of the year.

Use Cases

Agriculture: Schedule irrigation and harvest around actual solar peak
Architecture: Calculate sun angles for passive solar design
Health research: Annual civil-solar offset dataset for epidemiology
iCal integration: Pair with /solar/ical for a full calendar feed