In the completion of a
contract of sale of land made after the coming into operation of this Act 30
years is, subject to any stipulation to the contrary in the contract,
substituted as the period of commencement of title which a purchaser may
require in the place of 40 years, but earlier title than 30 years may be
required in cases similar to those in which earlier title than 40 years might
have been required immediately prior to the coming into operation of this Act.