gregorian

GREGORIAN  Converts digital Julian days to Gregorian calendar dates.  
       Although formally, 
       Julian days start and end at noon, here Julian days
       start and end at midnight for simplicity.
     
       In this convention, Julian day 2440000 begins at 
       0000 hours, May 23, 1968.

     Usage: [gtime]=gregorian(julian) 

        julian... input decimal Julian day number

        gtime is a six component Gregorian time vector
          i.e.   gtime=[yyyy mo da hr mi sec]
                 gtime=[1989 12  6  7 23 23.356]

0001 function [gtime]=gregorian(julian)
0002 %GREGORIAN  Converts digital Julian days to Gregorian calendar dates.
0003 %       Although formally,
0004 %       Julian days start and end at noon, here Julian days
0005 %       start and end at midnight for simplicity.
0006 %
0007 %       In this convention, Julian day 2440000 begins at
0008 %       0000 hours, May 23, 1968.
0009 %
0010 %     Usage: [gtime]=gregorian(julian)
0011 %
0012 %        julian... input decimal Julian day number
0013 %
0014 %        gtime is a six component Gregorian time vector
0015 %          i.e.   gtime=[yyyy mo da hr mi sec]
0016 %                 gtime=[1989 12  6  7 23 23.356]
0017  
0018 %        yr........ year (e.g., 1979)
0019 %        mo........ month (1-12)
0020 %        d........ corresponding Gregorian day (1-31)
0021 %        h........ decimal hours
0022 %
0023 %  calls S2HMS
0024  
0025       julian=julian+5.e-9;    % kludge to prevent roundoff error on seconds
0026 
0027 %      if you want Julian Days to start at noon...
0028 %      h=rem(julian,1)*24+12;
0029 %      i=(h >= 24);
0030 %      julian(i)=julian(i)+1;
0031 %      h(i)=h(i)-24;
0032 
0033       secs=rem(julian,1)*24*3600;
0034 
0035       j = floor(julian) - 1721119;
0036       in = 4*j -1;
0037       y = floor(in/146097);
0038       j = in - 146097*y;
0039       in = floor(j/4);
0040       in = 4*in +3;
0041       j = floor(in/1461);
0042       d = floor(((in - 1461*j) +4)/4);
0043       in = 5*d -3;
0044       m = floor(in/153);
0045       d = floor(((in - 153*m) +5)/5);
0046       y = y*100 +j;
0047       mo=m-9;
0048       yr=y+1;
0049       i=(m<10);
0050       mo(i)=m(i)+3;
0051       yr(i)=y(i);
0052       [hour,min,sec]=s2hms(secs);
0053       gtime=[yr(:) mo(:) d(:) hour(:) min(:) sec(:)];