func tai_from_list_file(dum)
 ;figure out the time for the list file name, return -1 if error
 name = removepath($t3d_list_file_name)
 ty,num_elem(name)
 ;just to be sure
 name = strloc(name, 'tri')
 name = strtrim(name)
 if num_elem(name) ne 16 then return, -1
 name = name(3:*)
 y1 = fix(name(0:3)
 mon1 = fix(name(4:5)
 dom1 = fix(name(6:7)
 d1 = doy(y1,mon1,dom1)
 ;;ty,'y1,mon1,dom1, d1 =', y1,mon1,dom1, d1
 h1 = fix(name(9:10)
 t1 = tai_from_date(y1, d1, h1, 0, 0)
 return, t1
 endfunc
 ;=======================================================