Convert Julian-Day-Number to Julian Century

Convert a Julian-Day number to a time in julian centuries since noon on January 1, 1900. The method follows Equation 15.1 in Reference 1. The example reproduces the Example 15.a of the same source, with fractional error 3e-8.

Usage

julianCenturyAnomaly(jd)

Arguments

jd

a julian day number, e.g. as given by julianDay().

Value

Julian century since noon on January 1, 1900.

References

1. Meeus, Jean. Astronomical Formulas for Calculators. Second Edition. Richmond, Virginia, USA: Willmann-Bell, 1982.

See also

Other things related to astronomy: angle2hms(), eclipticalToEquatorial(), equatorialToLocalHorizontal(), julianDay(), moonAngle(), siderealTime(), sunAngle(), sunDeclinationRightAscension()

Other things related to time: ctimeToSeconds(), julianDay(), numberAsHMS(), numberAsPOSIXct(), secondsToCtime(), unabbreviateYear()

Author

Dan Kelley

Examples

t <- ISOdatetime(1978, 11, 13, 4, 35, 0, tz = "UTC")
jca <- julianCenturyAnomaly(julianDay(t))
cat(format(t), "is Julian Century anomaly", format(jca, digits = 8), "\n")
#> 1978-11-13 04:35:00 is Julian Century anomaly 0.78865684