If the occupancy and use of a building or of land for which a Certificate of Occupancy has been issued is not commenced within six months after the date of such issuance or such period as the Zoning Official may authorize in writing because of the occurrence of conditions unforeseen at the time of issuance, such occupancy permit shall expire and a new occupancy permit shall be obtained before such occupancy and use are commenced.

No such extension of time for longer period than 90 days shall be authorized except upon the approval by a reviewing board.

All approvals by the Planning Board and Zoning Board of Adjustment shall expire two years after the adoption of a resolution of approval unless the applicant applies for an extension, as permitted, or unless construction or use of the premises has commenced within said year.