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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 2456293.520833. [ 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.
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).
The Julian day number is a simplified time-keeping system originally intended to ease calculation with historical dates which involve a diversity of local, idiosyncratic calendars. It was adopted by astronomers in the mid-1800s, and identifies each date as the integer number of days that have elapsed since a reference date ( "epoch" ), chosen ...
B.P. – for Before Present, specifically, the number of radiocarbon years before 1950. Julian day number – for counting days, not years, its era fixed at noon 1 January, 4713 BC in the proleptic Julian calendar. This equals 24 November, 4714 BC in the proleptic Gregorian calendar. From noon of this day to noon of the next day was day 0.
The need to correct the calendar arose from the realisation that the correct figure for the number of days in a year is not 365.25 (365 days 6 hours) as assumed by the Julian calendar but slightly less (c. 365.242 days). The Julian calendar therefore has too many leap years.
Thus there is no simple way to find an equivalent in the proleptic Julian calendar of a date quoted using either the Roman pre-Julian calendar or the Julian calendar before AD 8. The year 46 BC itself is a special case: because of the historical introduction of the Julian calendar in that year, it was allotted 445 days.
Then add the GMT correlation to the total number of days. 1,372,300 + 584,283 = 1,956,583. This number is a Julian day. To convert a Julian day to a Proleptic Gregorian calendar date: [61] From this number, subtract the nearest smaller Julian Day Number (in the table below), in this case 1,940,206, which corresponds to the year 600 CE.