//This file is part of SECONDO.

//Copyright (C) 2004, University in Hagen, Department of Computer Science, 
//Database Systems for New Applications.

//SECONDO is free software; you can redistribute it and/or modify
//it under the terms of the GNU General Public License as published by
//the Free Software Foundation; either version 2 of the License, or
//(at your option) any later version.

//SECONDO is distributed in the hope that it will be useful,
//but WITHOUT ANY WARRANTY; without even the implied warranty of
//MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//GNU General Public License for more details.

//You should have received a copy of the GNU General Public License
//along with SECONDO; if not, write to the Free Software
//Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package viewer.hoese;


/** this class provides transformations between julian and
    gregorian calendar */


public class JulianDate{


public static long toJulian(int year, int month, int day)
   /**
    * @return The Julian day number that begins at noon of
    * this day
    * Positive year signifies A.D., negative year B.C.
    * Remember that the year after 1 B.C. was 1 A.D.
    *
    * A convenient reference point is that May 23, 1968 noon
    * is Julian day 2440000.
    *
    * Julian day 0 is a Monday.
    *
    * This algorithm is from Press et al., Numerical Recipes
    * in C, 2nd ed., Cambridge University Press 1992
    */
   {  long jy = year;
      if (year < 0) jy++;
      long jm = month;
      if (month > 2) jm++;
      else
      {  jy--;
         jm += 13;
      }
      long jul = (long) (java.lang.Math.floor(365.25 * jy)
      + java.lang.Math.floor(30.6001*jm) + day + 1720995.0);
      long IGREG = 15 + 31*(10+12*1582);
         // Gregorian Calendar adopted Oct. 15, 1582
      if (day + 31 * (month + 12 * year) >= IGREG)
         // change over to Gregorian calendar
      {  long ja = (long)(0.01 * jy);
         jul += 2 - ja + (long)(0.25 * ja);
      }
      return jul-NULL_DAY;
   }


/** returns an array [year,month,day] */

public static int[] fromJulian(long j)
   /**
    * Converts a Julian day to a calendar date
    * @param j  the Julian date
    * This algorithm is from Press et al., Numerical Recipes
    * in C, 2nd ed., Cambridge University Press 1992
    */
   {  j=j+NULL_DAY;
      long ja = j;
      long JGREG = 2299161;
         /* the Julian date of the adoption of the Gregorian
            calendar
         */
      if (j >= JGREG)
      /* cross-over to Gregorian Calendar produces this
         correction
      */
      {  long jalpha = (long)(((float)(j - 1867216) - 0.25)
             / 36524.25);
         ja += 1 + jalpha - (long)(0.25 * jalpha);
      }
      long jb = ja + 1524;
      long jc = (long)(6680.0 + ((float)(jb-2439870) - 122.1)
          /365.25);
      long jd = (long)(365 * jc + (0.25 * jc));
      long je = (long)((jb - jd)/30.6001);
      long day = jb - jd - (long)(30.6001 * je);
      long month = je - 1;
      if (month > 12) month -= 12;
      long year = jc - 4715;
      if (month > 2) --year;
      if (year <= 0) --year;
      int[] res ={(int)year,(int)month,(int)day};
      return res;
   }

public static int NULL_DAY = 2451547; // make compatible with old hoese representation
}