All existing ordinances and all existing administrative rules, regulations and practices, if not inconsistent or in conflict with this charter, shall continue in full force and effect until repealed or modified by the council or other competent authority of the city. All ordinances, rules, regulations and practices that are inconsistent or in conflict with this charter shall, unless sooner repealed or modified, continue in full force and effect for a period of sixty days only, and at the end of that period shall to the extent of such inconsistency or conflict be of no further force or effect.