Within twenty-four months after the approval or conditional approval of the tentative map, a subdivider may cause his subdivision, or any part thereof, to be surveyed and a final map thereof prepared in conformance with the tentative map as approved by the planning commission, including conformance with any conditions attached to such approval. An extension of time for the filing of the final map may be granted by the planning commission for a period not to exceed one year, provided a written application is filed by the subdivider not less than thirty days in advance of the expiration date of the tentative map. Extensions shall not exceed a total of one year. In granting an extension, new conditions may be imposed and existing conditions may be modified as a condition to granting the extension. Subsequent modification or amendment of a tentative map shall not extend the total time limits imposed by this section. (Ord. 90-1 (part), 1990)