FUNCTION FndIDs, prefix, startT=startTime, idx=idx
;   ------------------------------------------------------------
;   ------------------------------------------------------------
;   ON_ERROR, 2     ;force a return to caller on error

;   Check prefix and !version:
    IF (!version.OS eq 'vms') THEN BEGIN    
      prefix = STRUPCASE(prefix)    ;VMS uses uppercase letters
    ENDIF ELSE BEGIN        ;must be some user friendly unix sys
      prefix = strlowcase(prefix)   ;unix files are generally lower
    ENDELSE

    IF (NOT KEYWORD_SET(startTime)) THEN BEGIN  ;load default value
      id = '*.*'
    ENDIF ELSE BEGIN        ;user specified start time
      IF (KEYWORD_SET(idx)) THEN BEGIN
        DATE2DOY, startTime, doy, yr    ;compute DOY and yr
        dayno = FIX(doy) + idx      ;increment start date
        IF (dayno gt 365) THEN BEGIN    
          IF ((FIX(yr) MOD 4) eq 0) THEN BEGIN  ;correct for leap yr
        IF (dayno gt 366) THEN BEGIN    ;new year
          yr = FIX(yr) +1
          dayno = dayno - 366
        ENDIF
          ENDIF ELSE BEGIN              ;not a leap year
            yr = FIX(yr) +1         ;new year
            dayno = dayno - 365
          ENDELSE
        ENDIF
        DOY2DATE, dayno, yr, month, day, sT
      ENDIF ELSE BEGIN
        sT = startTime
      ENDELSE
      id = sT + '.*'        ;append file extendsion name
    ENDELSE
    file = prefix + id
    a = FINDFILE(file)      ;Get list of files

;   Trim FileName Strings:
    st_pos = STRPOS(a(0),prefix) + 3    ;st_pos just after prefix
    len = 11                ;ok for now

    full_List = STRMID(a, st_pos, len)  ;trim all for IDS

    RETURN, full_List
    END