public function define_form_specific($form) {
        // Get the current calendar in use - see MDL-18375.
        $calendartype = \core_calendar\type_factory::get_calendar_instance();

        // Create variables to store start and end.
        list($year, $month, $day) = explode('_', date('Y_m_d'));
        $currentdate = $calendartype->convert_from_gregorian($year, $month, $day);
        $currentyear = $currentdate['year'];

        $arryears = $calendartype->get_years();

        // Add elements.
        $form->addElement('select', 'param1', get_string('startyear', 'profilefield_datetime'), $arryears);
        $form->setType('param1', PARAM_INT);
        $form->setDefault('param1', $currentyear);

        $form->addElement('select', 'param2', get_string('endyear', 'profilefield_datetime'), $arryears);
        $form->setType('param2', PARAM_INT);
        $form->setDefault('param2', $currentyear);

        $form->addElement('checkbox', 'param3', get_string('wanttime', 'profilefield_datetime'));
        $form->setType('param3', PARAM_INT);

        $form->addElement('hidden', 'startday', '1');
        $form->setType('startday', PARAM_INT);
        $form->addElement('hidden', 'startmonth', '1');
        $form->setType('startmonth', PARAM_INT);
        $form->addElement('hidden', 'startyear', '1');
        $form->setType('startyear', PARAM_INT);
        $form->addElement('hidden', 'endday', '1');
        $form->setType('endday', PARAM_INT);
        $form->addElement('hidden', 'endmonth', '1');
        $form->setType('endmonth', PARAM_INT);
        $form->addElement('hidden', 'endyear', '1');
        $form->setType('endyear', PARAM_INT);
        $form->addElement('hidden', 'defaultdata', '0');
        $form->setType('defaultdata', PARAM_INT);
    }