On written application therefor made by the listers or assessors of any town, with the approval of the selectboard of the town or mayor of the city, the several dates fixed by law and extended by section 4341 of this title or the charter of any municipal corporation, on or before which certain acts must be done relating to duties of listers and assessors, may be further extended by the Director and such extensions shall be in writing.
32 V.S.A. § 4342