bat-8.x-1.x-dev/modules/bat_event_ui/bat_event_ui.routing.yml

bat_event_ui.calendar:
  path: '/admin/bat/calendar/{unit_type}/{event_type}'
  defaults:
    _controller: '\Drupal\bat_event_ui\Controller\BatEventUIController::calendarPage'
    _title: 'Calendar'
  requirements:
    _permission: 'administer calendar events'