Work out julian date instantly with clear inputs, formula shown and shareable results.
The Julian date counts days continuously from noon on 1 January 4713 BC, which removes all calendar irregularities from astronomical calculations. 1 January 2026 at 12:00 UT is JD 2461042.0. The modified form subtracts 2400000.5 to give smaller numbers starting at midnight, and days since J2000.0 is the epoch most modern ephemerides use.
Julian date
JD = Unix days + 2440587.5 + hour / 24
Modified Julian date
MJD = JD - 2400000.5
So that a night's observing session falls within a single Julian day, which was convenient before electronic records.
The standard epoch, JD 2451545.0 - 1 January 2000 at 12:00 TT. Star coordinates and orbital elements are referred to it.