function ut2td, ut
;
; Given a scalar or array of Universal Time Julian Day Numbers,
; return the corresponding Dynamic Time Julian Day Numbers.
;
; B. Knapp, 2002-12-18
;
; RCS Data:
;
; $Header$
;
; $Log$
;
; Print usage?
  n = n_elements( ut )
  if n eq 0 then begin
     print, '     td = ut2td( ut )'
     return, ' '
  endif
;
; Use 32-bit or 64-bit shareable object library?
  mbits = ((!version.release ge 5.4) ? !version.memory_bits : 32)
  dll = getenv('bgkroot')+string(mbits,"('/lib/astron',i2,'.so')")
;
; Define output and then call the Fortran subroutine
  ut_loc = double( ut )
  td = dblarr( n )
  result = call_external( dll, 'ut2td_arg_', n, ut_loc, td )
;
; Return scalar or array, according to argument ut
  if (size( ut ))[0] eq 0 then $
     return, td[0] $
  else $
     return, td
  end