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If conversion takes you past a February 29 that exists only in the Julian calendar, then February 29 is counted in the difference. Years affected are those which divide by 100 without remainder but do not divide by 400 without remainder (e.g., 1900 and 2100 but not 2000).
In astronomy and celestial navigation, an ephemeris (/ ɪ ˈ f ɛ m ər ɪ s /; pl. ephemerides / ˌ ɛ f ə ˈ m ɛr ɪ ˌ d iː z /; from Latin ephemeris 'diary', from Ancient Greek ἐφημερίς (ephēmerís) 'diary, journal') [1] [2] [3] is a book with tables that gives the trajectory of naturally occurring astronomical objects and artificial satellites in the sky, i.e., the position ...
A calendrical calculation is a calculation concerning calendar dates. Calendrical calculations can be considered an area of applied mathematics. Some examples of calendrical calculations: Converting a Julian or Gregorian calendar date to its Julian day number and vice versa (see § Julian day number calculation within that article for details).
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 ...
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]
Raphael's Ephemeris was issued as a separate publication after Smith’s death, whilst others adopted and continued with the name 'Raphael'. The "second Raphael" was John Palmer (1807–1837), a former student of Smith's, who edited Raphael's Sanctuary of the Astral Art in 1834; the third was a Mr. Medhurst, the editor of the Prophetic ...
The JPL ephemeris time argument T eph is within a few milliseconds of TT. TT is slightly ahead of UT1 (a refined measure of mean solar time at Greenwich) by an amount known as Δ T = TT − UT1. Δ T was measured at +67.6439 seconds (TT ahead of UT1) at 0 h UTC on 1 January 2015; [ 16 ] and by retrospective calculation, Δ T was close to zero ...
The mean tropical year in 2000 was 365.24219 ephemeris days, each ephemeris day lasting 86,400 SI seconds. [3] This is 365.24217 mean solar days . [ 4 ] For this reason, the calendar year is an approximation of the solar year: the Gregorian calendar (with its rules for catch-up leap days ) is designed so as to resynchronise the calendar year ...