;------------------------------------------------------------- ;+ ; NAME: ; YDN2MD ; PURPOSE: ; Convert from year and day number of year to month and day of month. ; CALLING SEQUENCE: ; YDN2MD,yr,dy,m,d ; INPUTS: ; yr = 4 digit year (like 1988), integer scalar ; dy = day number in year (like 310), integer scalar or vector ; ; OUTPUTS: ; m = month number (1-12, e.g. 11 = Nov) ; d = day of month (like 5). ; Note: On error returns m = d = -1. ; ; EXAMPLE: ; Find the month/day of days 155 and 255 in the year 2001 ; ; IDL> ydn2md, 2001, [155,255], m, d ; ==> m = [6,9] & d = [4,12] ; = June 4 and September 12 ; ; MODIFICATION HISTORY: ; Adapted from Johns Hopkins University/Applied Physics Laboratory ; Update to use VALUE_LOCATE, W. Landsman January 2001 ;- ;------------------------------------------------------------- PRO YDN2MD,YR,DY,M,D, help=hlp IF (N_PARAMS() LT 4) or keyword_set(hlp) THEN BEGIN PRINT,' Convert from year and day number of year to month '+\$ 'and day of month.' PRINT,' ydn2md,yr,dy,m,d' PRINT,' yr = year (like 1988), scalar input' PRINT,' dy = day number in year (like 310), scalar or vector input' PRINT,' m = month number (like 11 = Nov). out' PRINT,' d = day of month (like 5). out' PRINT,' Note: On error returns m = d = -1.' RETURN ENDIF ; Days before start of each month. YDAYS = [0,31,59,90,120,151,181,212,243,273,304,334,366] + 1 LEAP = (((YR MOD 4) EQ 0) AND ((YR MOD 100) NE 0)) OR \$ ((YR MOD 400) EQ 0) IF LEAP THEN YDAYS[2] = YDAYS[2:*] + 1 M = VALUE_LOCATE(YDAYS, DY) + 1 D = DY - YDAYS[M-1] + 1 BAD = WHERE(M GT 12, NBAD) IF NBAD GT 0 THEN BEGIN M[BAD] = -1 D[BAD] = -1 MESSAGE,'Error in Day Number',/CON ENDIF RETURN END