juldate {astrolibR}R Documentation

Convert from calendar to Reduced Julian Date


Convert from calendar to Reduced Julian Date





3 to 6-element vector containing year,month (1-12),day, and optionally hour, minute, and second. These are all values of Universal Time. Year should be supplied with all digits. Years B.C should be entered as negative numbers (and note that Year 0 did not exist). If hour, minute or seconds are not supplied, they will default to 0.


Julian Day Number is a count of days elapsed since Greenwich mean noon on 1 January 4713 B.C. The Julian Date (JD) is the Julian day number followed by the fraction of the day elapsed since the preceding noon. The output of this function is the Reduced Julian Date

RJD = JD - 2400000.0

The function helio_jd can be used after juldate if a heliocentric Julian date is required. The function daycnv converts dates in the opposite direction from Julian dates to Gragorian calendar dates.

The algorithm is obtained from Sky and Telescope April 1981



Reduced Julian Date, scalar


Adapted from IUE RDAF (S. Parsons) 8-31-87

R adaptation by Arnab Chakraborty (June 2013)

See Also

helio_jd daycnv


#  The date of 25-DEC-2006 06:25 UT 
#  Result:   JD = 54094.7673611

juldate(c(2006, 12, 25, 6, 25)) 
juldate(c(2006, 12, 25.2673611)) 

[Package astrolibR version 0.1 Index]