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The Julian date (JD) of any instant is the Julian day number plus the fraction of a day since the preceding noon in Universal Time. Julian dates are expressed as a Julian day number with a decimal fraction added. [8] For example, the Julian Date for 00:30:00.0 UT January 1, 2013, is 2 456 293.520 833. [9]
No guidance is provided about conversion of dates before March 5, -500, or after February 29, 2100 (both being Julian dates). For unlisted dates, find the date in the table closest to, but earlier than, the date to be converted. Be sure to use the correct column. If converting from Julian to Gregorian, add the number from the "Difference" column.
The Barycentric Julian Date (BJD) is the Julian Date (JD) corrected for differences in the Earth's position with respect to the barycentre of the Solar System. Due to the finite speed of light , the time an astronomical event is observed depends on the changing position of the observer in the Solar System.
The Julian Date is a linear transformation of the raw count of seconds represented by the variable TCG, so this form of the equation is not simplified. The use of a Julian Date specifies the epoch fully. The above equation is often given with the Julian Date 2443 144.5 for the epoch, but that is inexact (though inappreciably so, because of the ...
Barycentric Dynamical Time ( TDB, from the French Temps Dynamique Barycentrique) is a relativistic coordinate time scale, intended for astronomical use as a time standard to take account of time dilation [1] when calculating orbits and astronomical ephemerides of planets, asteroids, comets and interplanetary spacecraft in the Solar System.
In addition, an epoch optionally prefixed by "J" and designated as a year with decimals (2000 + x), where x is either positive or negative and is quoted to 1 or 2 decimal places, has come to mean a date that is an interval of x Julian years of 365.25 days away from the epoch J2000 = JD 2451545.0 (TT), still corresponding (in spite of the use of ...
Julian calendar. The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts of Oriental Orthodoxy as well as by the Amazigh people (also known as the Berbers).
Heliocentric Julian Day. The Heliocentric Julian Date ( HJD) is the Julian Date (JD) corrected for differences in the Earth 's position with respect to the Sun. When timing events that occur beyond the Solar System, due to the finite speed of light, the time the event is observed depends on the changing position of the observer in the Solar ...