class DatetimeHooks

class DatetimeHooks {
    
    /**
     * Implements hook_help().
     */
    public function help($route_name, RouteMatchInterface $route_match) {
        switch ($route_name) {
            case 'help.page.datetime':
                $output = '';
                $output .= '<h2>' . t('About') . '</h2>';
                $output .= '<p>' . t('The Datetime module provides a Date field that stores dates and times. It also provides the Form API elements <em>datetime</em> and <em>datelist</em> for use in programming modules. See the <a href=":field">Field module help</a> and the <a href=":field_ui">Field UI module help</a> pages for general information on fields and how to create and manage them. For more information, see the <a href=":datetime_do">online documentation for the Datetime module</a>.', [
                    ':field' => Url::fromRoute('help.page', [
                        'name' => 'field',
                    ])->toString(),
                    ':field_ui' => \Drupal::moduleHandler()->moduleExists('field_ui') ? Url::fromRoute('help.page', [
                        'name' => 'field_ui',
                    ])->toString() : '#',
                    ':datetime_do' => 'https://www.drupal.org/documentation/modules/datetime',
                ]) . '</p>';
                $output .= '<h2>' . t('Uses') . '</h2>';
                $output .= '<dl>';
                $output .= '<dt>' . t('Managing and displaying date fields') . '</dt>';
                $output .= '<dd>' . t('The <em>settings</em> and the <em>display</em> of the Date field can be configured separately. See the <a href=":field_ui">Field UI help</a> for more information on how to manage fields and their display.', [
                    ':field_ui' => \Drupal::moduleHandler()->moduleExists('field_ui') ? Url::fromRoute('help.page', [
                        'name' => 'field_ui',
                    ])->toString() : '#',
                ]) . '</dd>';
                $output .= '<dt>' . t('Displaying dates') . '</dt>';
                $output .= '<dd>' . t('Dates can be displayed using the <em>Plain</em> or the <em>Default</em> formatter. The <em>Plain</em> formatter displays the date in the <a href="http://en.wikipedia.org/wiki/ISO_8601">ISO 8601</a> format. If you choose the <em>Default</em> formatter, you can choose a format from a predefined list that can be managed on the <a href=":date_format_list">Date and time formats</a> page.', [
                    ':date_format_list' => Url::fromRoute('entity.date_format.collection')->toString(),
                ]) . '</dd>';
                $output .= '</dl>';
                return $output;
        }
    }

}