Description Usage Arguments Value Author(s) References See Also Examples
Convert a POSIXt time to a Julian day, using the method provided in
Chapter 3 of Meeus (1982). It should be noted that
Meeus and other astronomical treatments use fractional days, whereas the
present code follows the R convention of specifying days in whole numbers,
with hours, minutes, and seconds also provided as necessary. Conversion is
simple, as illustrated in the example for 1977 April 26.4, for which Meeus
calculates julian day 2443259.9. Note that the R documentation for
julian
suggests another formula, but the point of the present
function is to match the other Meeus formulae, so that suggestion is ignored
here.
1 2 
t 
a time, in POSIXt format, e.g. as created by

year 
year, to be provided along with 
month 
month, numbered with January being 1. 
day 
day in month, starting at 1. 
hour 
hour of day. 
min 
minute of hour 
sec 
second of hour 
tz 
timezone 
A JulianDay number, in astronomical convention as explained in Meeus.
Dan Kelley
Meeus, Jean, 1982. Astronomical formuae for Calculators. WillmannBell. Richmond VA, USA. 201 pages
Other things related to astronomy: eclipticalToEquatorial
,
equatorialToLocalHorizontal
,
julianCenturyAnomaly
,
moonAngle
, siderealTime
,
sunAngle
Other things related to time: ctimeToSeconds
,
julianCenturyAnomaly
,
numberAsHMS
, numberAsPOSIXct
,
secondsToCtime
,
unabbreviateYear
1 2 3 
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