function xrt_find_dark, t0 ,t1, dir=dir,count=count,quiet=quiet
;+
;   Name: xrt_find_dark
;
;   Purpose: return list of xrt darks within +/- two days of t0 
;            If t1 is provided then searches for all darks between
;            t0 & t1
;
;   Input Parameters:
;      t0:  Date to search in a format. Yes, that's right, the date is
;           in a format. What format? ---I'm not exactly sure. But I would
;           think that any form that the function anytim() outputs 
;           would be an acceptable format to put the date in. See Examples
;
;   Calling Sequence:
;      filelist=xrt_find_dark(t0, [t1,dir=dir, count=count, quiet=quiet] )
;
;   Keyword Parameters:
;   dir: The topmost directory for the xrt archive
;       Program assumes that the data is arranged by
;       dir/YYYY/MM/DD/H"hhhh"/*.fits
;
;    count: The number of files fount
;    
;   Calling Examples:
;    darks=xrt_find_dark('26-oct-2006','29-oct-2006')
;    darks=xrt_find_dark('26-oct-06',dir='/my/copy/xrt/data')
;    darks=xrt_find_dark('27-oct-06',/quiet,count=count)
;
;   If no files are found it returns a value of -1.
; 
;   History:
;      30-Oct-2006 P.R. Jibben bootlegged from trace_files by S.L.Freeland 
;
;
; Personal Note for future changes:
; USED by TRACE if there was an enviornment variable. There will be
; one for XRT just not yet.
;topenv='TRACE_I1_DIR'
;toptrace=str2arr(get_logenv(topenv))
;toptrace=str_replace(toptrace,'tri',lprefix)

if not keyword_set(dir) then topxrt='/archive/hinode/xrt/level0/' else topxrt=dir  

if not file_exist(topxrt(0)) then begin 
   box_message,'Need to define '+topxrt +' (parent of XRT data subdirectories)'
   return,''
endif

; XRT archive listed as YYYY/MM/DD/"H"hhhh/*.fits
; Based on t0 & t1 determine what Year(s), Month(s) and
; day(s) the program searches.

;; if times passed, form subdirectories
      if n_elements(t1) eq 0 then grid=timegrid(t0,days=[-2,-1,0,1,2],/string) else $
      grid=timegrid(timegrid(t0,hour=0,/string),t1,days=1,/quiet)

      dates=strmid(anytim(grid,/ecs),0,11)
      dir_dd=concat_dir(topxrt,dates)
      dir=dir_dd[where(file_exist(dir_dd) eq 1)]
      hours=file_list(dir,'H*',/quiet)
      files=file_list(hours,'*d*.fits',/quiet)

if ((n_elements(files) eq 1) and (files[0] eq '')) then begin
count=0
files=fix('-1')
endif else begin
count=n_elements(files)
endelse

if not keyword_set(quiet) then begin
print,'Searching Directories:'
hprint,dir
print,''
print,'Search Complete   Found: '+strcompress(count,/remove_all)+' files'
endif

return,files
end