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Julian within its name indicates that other Julian epochs can be a number of Julian years of 365.25 days each before or after J2000.0. For example, the future epoch J2100.0 will be exactly 36,525 days (one Julian century) from J2000.0 at 12:00 TT on January 1, 2100 (the dates will still agree because the Gregorian century 2000–2100 will have ...
The term Julian date may also refer, outside of astronomy, to the day-of-year number (more properly, the ordinal date) in the Gregorian calendar, especially in computer programming, the military and the food industry, [10] or it may refer to dates in the Julian calendar. For example, if a given "Julian date" is "October 5, 1582", this means ...
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 System. Before multiple ...
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 ...
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. Before multiple observations can be ...
See also Julian year (astronomy).) Like the Besselian epoch, an arbitrary Julian epoch is therefore related to the Julian date by J = 2000 + (Julian date − 2451545.0) ÷ 365.25. The IAU decided at their General Assembly of 1976 [8] that the new standard equinox of J2000.0 should be used starting in 1984. Before that, the equinox of B1950.0 ...
11 must-see astronomy events in 2025 From planetary meet-ups to the first total lunar eclipse in three years, here are the top astronomy events to look for throughout 2025:
Astronomers use the Julian calendar for years before 1582, including the year 0, and the Gregorian calendar for years after 1582, as exemplified by Jacques Cassini (1740), [2] Simon Newcomb (1898) [3] and Fred Espenak (2007). [4] The prefix AD and the suffixes CE, BC or BCE (Common Era, Before Christ or Before Common Era) are dropped. [1]