cal2jd.R

source("fix.R")

cal2jd <- function(yr,mn,dy){
  # % CAL2JD  Converts calendar date to Julian date using algorithm
  # %   from "Practical Ephemeris Calculations" by Oliver Montenbruck
  # %   (Springer-Verlag, 1989). Uses astronomical year for B.C. dates
  # %   (2 BC = -1 yr). Non-vectorized version. See also DOY2JD, GPS2JD,
  # %   JD2CAL, JD2DOW, JD2DOY, JD2GPS, JD2YR, YR2JD.
  # % Version: 1999-04-24
  # % Usage:   jd=cal2jd(yr,mn,dy)
  # % Input:   yr - calendar year (4-digit including century)
  # %          mn - calendar month
  # %          dy - calendar day (including factional day)
  # % Output:  jd - jJulian date
  # 
  # % Copyright (c) 2011, Michael R. Craymer
  # % All rights reserved.
  # % Email: mike@craymer.com
  
  
#   if (mn < 1 | mn > 12){ 
#     "Choose another data set. No mtcars please!"
#     
#     
#   }
  # if (dy < 1){
  #   if (mn == 2 & dy > 29) | (any(mn == [3 5 9 11]) & dy > 30) | (dy > 31){
  # 
  # return
  # }
  # }
  
  if (mn > 2){
    y = yr;
    m = mn;}
  else{
    y = yr - 1;
    m = mn + 12;}
  
  date1=4+31*(10+12*1582);   #% Last day of Julian calendar (1582.10.04)
  date2=15+31*(10+12*1582);  #% First day of Gregorian calendar (1582.10.15)
  date=dy+31*(mn+12*yr);
  if (date <= date1){
  b = -2;}
  if (date >= date2){
  b = fixVal(y/400) - fixVal(y/100);}
  else{
  
  return(-2);
  }
  if (y > 0){
  jd = fixVal(365.25*y) + fixVal(30.6001*(m+1)) + b + 1720996.5 + dy;}
  else{
    jd = fixVal(365.25*y-0.75) + fixVal(30.6001*(m+1)) + b + 1720996.5 + dy;
  }
  
  return(jd)
}