JDC to be converted to a Gregorian calendar date.
the Gregorian calendar date created from the given JDC.
Converts a JDC to an Islamic calendar date.
Algorithm from: Jean Meeus, Astronomical Algorithms, 1998, 75pp.
The first day of the Islamic calendar according to this algorithm is July 16th, 622 CE (Julian; JDC = 1948439.5). This is in agreement with the widely used tables of Wuestenfeld et al., Wuestenfeld-Mahler'sche Vergleichungs-Tabellen zur muslimischen und iranischen Zeitrechnung, 1961. However, it is well known that these calendar dates may be off by 1 to 2 days in comparison to the calendar that was actually used, especially if historical dates are concerned. There are two more points of concern: Sura 9, 36-37 of the Koran suggests that a lunar calendar without intercalation was applied from year 10 of the Hijra onwards only; earlier on, probably a luni-solar calendar was used. This algorithm assumes that a lunar calendar without any intercalation started in year 1 of the Hijra. Secondly, in many countries the first actual sighting of the lunar crescent was decisive for the beginning of a new month up to quite recent times, but not a regular scheme. This introduces a dependency on the location: a new Islamic calendar month may have started on different days in different locations. Unambiguous conversion of historical Islamic dates into Julian or Gregorian calendar dates or vice cersa can only be achieved if the day of the week is known in addition.
JDC to be converted to an Islamic calendar date.
Islamic calendar date created from given JDC.
Converts a JDC to a Julian Calendar date.
Conversion algorithm from: Jean Meeus, Astronomical Algorithms, 1998, 63pp.
There is a year 0.
JDC to be converted to a Julian calendar date.
Julian calendar date created from given JDC.
Converts a JDN to a Gregorian calendar date.
the given JDN.
the Gregorian calendar date created from the given JDN.
Converts a JDN to an Islamic calendar date.
JDN to be converted to an Islamic calendar date.
@returns Islamic calendar date created from given JDN.
Converts a JDN to a Julian calendar date.
JDN to be converted to a Julian calendar date.
Julian calendar date created from given JDN.
Determine the day of week from the given JDN. Works only for calendars which use the 7 day week with Sunday to Saturday.
Algorithm from: Jean Meeus: Astronomical Algorithms, 1998, p. 65.
given JDC.
the number of the day of the week for the given JDC (0 Sunday, 1 Monday, 2 Tuesday, 3 Wednesday, 4 Thursday, 5 Friday, 6 Saturday).
Converts a Gregorian calendar date to a JDC.
Conversion algorithm from: Jean Meeus, Astronomical Algorithms, 1998, 60pp.
There is a year 0.
Gregorian calendar date to be converted to JDC.
the JDC representing the given Gregorian calendar date.
Converts a Gregorian calendar date to a JDN.
Gregorian calendar date to be converted to JDN.
the JDN representing the given Gregorian calendar date.
Converts an Islamic calendar date to a JDC.
Algorithm from: Jean Meeus, Astronomical Algorithms, 1998, 73pp.
The first day of the Islamic calendar according to this algorithm is July 16th, 622 CE (Julian; JDC = 1948439.5). This is in agreement with the widely used tables of Wuestenfeld et al., Wuestenfeld-Mahler'sche Vergleichungs-Tabellen zur muslimischen und iranischen Zeitrechnung, 1961. However, it is well known that these calendar dates may be off by 1 to 2 days in comparison to the calendar that was actually used, especially if historical dates are concerned. There are two more points of concern: Sura 9, 36-37 of the Koran suggests that a lunar calendar without intercalation was applied from year 10 of the Hijra onwards only; earlier on, probably a luni-solar calendar was used. This algorithm assumes that a lunar calendar without any intercalation started in year 1 of the Hijra. Secondly, in many countries the first actual sighting of the lunar crescent was decisive for the beginning of a new month up to quite recent times, but not a regular scheme. This introduces a dependency on the location: a new Islamic calendar month may have started on different days in different locations. Unambiguous conversion of historical Islamic dates into Julian or Gregorian calendar dates or vice cersa can only be achieved if the day of the week is known in addition.
Islamic calendar date to be converted to JDC.
JDC representing the given Islamic calendar date.
Converts an Islamic calendar date to a JDN.
Islamic calendar date to be converted to JDN.
JDN representing the given Islamic calendar date.
Converts a Julian calendar date to a JDC.
Conversion algorithm from: Jean Meeus, Astronomical Algorithms, 1998, 60pp.
There is a year 0.
Julian calendar date to be converted to JDC.
JDC representing the given Julian calendar date.
Converts a Julian calendar date to a JDN.
Julian calendar date to be converted to JDN.
JDN representing the given Julian calendar date.
Removes the fraction from a given number (https://stackoverflow.com/questions/4912788/truncate-not-round-off-decimal-numbers-in-javascript/9232092#9232092). This also works for negative numbers.
1.2 -> 1 -3.2 -> -3
the number whose fraction is to be removed.
given number without fractions.
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Converts a JDC to a Gregorian Calendar date.
Conversion algorithm from: Jean Meeus, Astronomical Algorithms, 1998, 63pp.
There is a year 0.