;***************************************************
;  This program takes in the year month and day.  It 
;  calculates the day of the year
;***************************************************

pro julian_date,year,month,day,juldate

;year=2007
;month=4
;day=13

;******************************
;  Check if the year is a leap year
;******************************

leap_flag=0  ;not a leap year
check4=(year) mod 4  ;years divisible by 4 are leap years, unless...........
check100=(year) mod 100  ;years also divisible by  100 are not leap years, except.......
check400=(year)mod 400  ;years divisible by 400 are leap years.
if (  (check4 eq 0 and check100 ne 0) or (check400 eq 0) ) then leap_flag=1  ;leap year

;******************************
;  Make an array of the number of days
;******************************

if leap_flag eq 0 then begin
           ; J  F  M  A  M  J  J  A  S  O  N  D
  num_days=[31,28,31,30,31,30,31,31,30,31,30,31]
endif else if leap_flag eq 1 then begin
  num_days=[31,29,31,30,31,30,31,31,30,31,30,31]
endif

;  Sum up the months of days
if month-2 ge 0 then juldate=total(num_days[0:month-2]) else juldate=0

;  Add on the extra days
juldate=juldate+day

;  Make it an integer
juldate=fix(juldate)

;print,year,month,day
;print,juldate
;print,'leap_flag',leap_flag

return
end