function _createElements() {
        $attributes = $this->getAttributes();
        if (is_null($attributes)) {
            $attributes = array();
        }
        if (!isset($attributes['size'])) {
            $attributes['size'] = 3;
        }
        $this->_elements = array();
        // E_STRICT creating elements without forms is nasty because it internally uses $this
        $number = $this->createFormElement('text', 'number', get_string('time', 'form'), $attributes, true);
        $number->set_force_ltr(true);
        $this->_elements[] = $number;
        unset($attributes['size']);
        $this->_elements[] = $this->createFormElement('select', 'timeunit', get_string('timeunit', 'form'), $this->get_units(), $attributes, true);
        // If optional we add a checkbox which the user can use to turn if on
        if($this->_options['optional']) {
            $this->_elements[] = $this->createFormElement('checkbox', 'enabled', null, get_string('enable'), $this->getAttributes(), true);
        }
        foreach ($this->_elements as $element){
            if (method_exists($element, 'setHiddenLabel')){
                $element->setHiddenLabel(true);
            }
        }
    }