function clearField(id)
{
  if (document.getElementById)
    field = document.getElementById(id);

  else if (document.all)
    field = eval('document.all.' + id);

  if (
      ('DD.MM.RRRR' == field.value) ||
      ('MM.RRRR'    == field.value) ||
      ('DD.MM.YYYY' == field.value) ||
      ('MM.YYYY'    == field.value) ||
      ('TT.MM.JJJJ' == field.value) ||
      ('MM.JJJJ'    == field.value) ||
      (0            == field.value)
      )
    field.value = '';

}