pro julian1200_sbsp, iy, month, iday, jul ; julian day number at 0 h ut=0.5+julian(iday,month,iyr). md = [0,31,59,90,120,151,181,212,243,273,304,334] md = long(md) ; iyr = iy ; if(iyr lt 50) then iyr = iyr+2000 ; if(iyr le 100) then iyr = iyr+1900 leap = 0 jyr = iyr-1600 i1 = jyr/400 i2 = (jyr-400*i1)/100 i3 = (jyr-400*i1-100*i2)/4 jul = 2305448+365*jyr+97*i1+24*i2+i3 if (jyr mod 4) eq 0 then leap = 1 if (jyr mod 100) eq 0 then leap = 0 if (jyr mod 400) eq 0 then leap = 1 jul = jul+md(month-1)+iday if(month le 2) then jul = jul-leap ; leap=1 in leap years. return end