Environment Libraries allows themers to manage external css & js through the a Drupal admin UI & optionally with contexts (the recommended approach). Files support multiple versions based on prod/stage/dev environments for easier development on production instances. A basic role based permission allows access to non-production versions of a library.
Navigate Administration » Configuration » Date Popup (admin/config/date/date_popup), select "jQuery UI Timepicker" in the options list and save settings. So this is the only available option added by the Date Popup Timepicker module for now and it's full name is jQuery UI Timepicker (By François Gélinas) timepicker library: https://fgelinas.com/code/timepicker/