{"placeholder":"Made-up values to show the page layout. This is not test data.","algorithm":"astronomical-time","publishedDate":"2026-01-01","expiresDate":"2027-12-31","earthModel":"WGS84","sources":[{"role":"Method","name":"Astronomical Algorithms, 2nd edition, 1998","by":"Jean Meeus","url":"","licence":""},{"role":"ΔT","name":"Earth orientation data","by":"IERS","url":"https://www.iers.org/","licence":"⚠️ Terms not checked yet"},{"role":"Reference","name":"Astronomical Applications API","by":"US Naval Observatory","url":"https://aa.usno.navy.mil/data/api","licence":"Public domain"}],"operations":[{"id":"julianDay","gives":"The Julian day of an instant","inputs":["instantUtc"],"outputs":["julianDay"]},{"id":"calendarDate","gives":"The calendar date of a Julian day","inputs":["julianDay"],"outputs":["date","calendar"]},{"id":"deltaT","gives":"ΔT for a date","inputs":["decimalYear"],"outputs":["deltaTInSeconds"]},{"id":"siderealTime","gives":"Mean sidereal time at Greenwich and at a longitude","inputs":["instantUtc","longitudeInDegrees"],"outputs":["greenwichSiderealTimeInHours","localSiderealTimeInHours"]},{"id":"horizontal","gives":"A sky position as azimuth and altitude from a place","inputs":["rightAscensionInHours","declinationInDegrees","latitudeInDegrees","longitudeInDegrees","instantUtc"],"outputs":["azimuthInDegrees","altitudeInDegrees"]}],"fields":{"latitudeInDegrees":"−90 to 90, WGS84, north positive","longitudeInDegrees":"−180 to 180, WGS84, east positive","instantUtc":"An instant, ISO 8601 in UTC, like 2026-01-01T00:00:00Z","julianDay":"Days since noon UTC on 1 January 4713 BC, with a fraction","date":"A calendar date, YYYY-MM-DD, astronomical years (1 BC is 0000)","calendar":"gregorian from 1582-10-15, julian before","decimalYear":"The year plus the fraction elapsed","deltaTInSeconds":"Uniform time minus Earth-rotation time","greenwichSiderealTimeInHours":"0 to 24","localSiderealTimeInHours":"0 to 24","rightAscensionInHours":"0 to 24, a sky position's east–west angle","declinationInDegrees":"−90 to 90, a sky position's angle north of the celestial equator","azimuthInDegrees":"0 to 360, clockwise from north","altitudeInDegrees":"−90 to 90, up from the horizon"},"tolerances":{"julianDay":"0.00001","deltaTInSeconds":"1","greenwichSiderealTimeInHours":"0.0001","localSiderealTimeInHours":"0.0001","azimuthInDegrees":"0.01","altitudeInDegrees":"0.01"},"cases":[{"id":"placeholder-1","operation":"julianDay","tags":["hand"],"input":{"instantUtc":"2026-01-01T00:00:00Z"},"expected":{"julianDay":1234567.5}},{"id":"placeholder-2","operation":"calendarDate","tags":["edge","hand"],"input":{"julianDay":1234567.5},"expected":{"date":"1582-10-15","calendar":"gregorian"}},{"id":"placeholder-3","operation":"deltaT","tags":["reference"],"input":{"decimalYear":2026.0},"expected":{"deltaTInSeconds":12.3}},{"id":"placeholder-4","operation":"horizontal","tags":["reference"],"input":{"rightAscensionInHours":1.23,"declinationInDegrees":45.6,"latitudeInDegrees":11.11,"longitudeInDegrees":22.22,"instantUtc":"2026-01-01T00:00:00Z"},"expected":{"azimuthInDegrees":123.45,"altitudeInDegrees":35.67}}]}