# File app/models/timeslot.rb, line 184
  def tolerances_correctly_formatted
    [:tolerance_pre, :tolerance_post].each do |attr| 
      field = self.send(attr)
      field.nil? or field.blank? or field =~ /^\d\d?:\d\d(:\d\d)?$/ or
        errors.add(field, _('Wrong format (should be hh:mm or hh:mm:ss)'))
    end
  end