Customs exemption notification extension prolongs applicability period under statutory powers for public interest, altering prior expiry date. Exercising authority under section 25(1) of the Customs Act, 1962, the Central Government amended paragraph 2 of Notification No.39/2005 Customs by substituting the previously specified expiry date with a later date, thereby prolonging the notification's applicability; the amendment was issued as Notification No.29/2007 Customs and published in the Gazette.