;------------------------------------------------------------- ;+ ; NAME: ; YMD2JD ; PURPOSE: ; From Year, Month, and Day compute Julian Day number. ; CATEGORY: ; CALLING SEQUENCE: ; jd = ymd2jd(y,m,d) ; INPUTS: ; y = Year (like 1987). in ; m = month (like 7 for July). in ; d = month day (like 23). in ; KEYWORD PARAMETERS: ; OUTPUTS: ; jd = Julian Day number (like 2447000). out ; COMMON BLOCKS: ; NOTES: ; MODIFICATION HISTORY: ; R. Sterner, 23 June, 1985 --- converted from FORTRAN. ; Johns Hopkins University Applied Physics Laboratory. ; RES 18 Sep, 1989 --- converted to SUN ; ; Copyright (C) 1985, Johns Hopkins University/Applied Physics Laboratory ; This software may be used, copied, or redistributed as long as it is not ; sold and this copyright notice is reproduced on each copy made. This ; routine is provided as is without any express or implied warranties ; whatsoever. Other limitations apply as described in the file disclaimer.txt. ;- ;------------------------------------------------------------- function ymd2jd, iy, im, id, help=hlp if (n_params(0) LT 3) or keyword_set(hlp) then begin print,' From Year, Month, and Day compute Julian Day number.' print,' jd = ymd2jd(y,m,d)' print,' y = Year (like 1987). in' print,' m = month (like 7 for July). in' print,' d = month day (like 23). in' print,' jd = Julian Day number (like 2447000). out' return, -1 endif y = long(iy) m = long(im) d = long(id) jd = 367*y-7*(y+(m+9)/12)/4-3*((y+(m-9)/7)/100+1)/4 $ +275*m/9+d+1721029 return, jd end