[Extension of time for assessment payment or stock sale;

restrictions.] The dates fixed in any notice of assessment, or notice of delinquent sale, may be extended from time to time for not more than thirty days, by order of the directors, entered in the journal of their proceedings; but no order extending the time for the performance of any act specified in any notice shall be effectual unless notice of such extension or postponement is appended to and published with the notice to which the order relates.