30 CAP. 400] Patents he may amend the patent by substituting for the name of that person the name of the person entitled thereto according to law, and the patent shall have effect, and shall be deemed always to have had effect, accordingly. Date of patent 27. (1) Subject to the provisions of this Act, the date of a patent shall be­ (a) in the case of a patent granted under this Act, the effective date of the application therefor; (b) in the case of a patent granted under the Patents (Southern Rhodesia) Act, Chapter 208 of the 1948 Edition of the Laws, the date the patent was sealed; (c) in the case of a patent registered under the Registration of United Kingdom Patents Act, Chapter 205 of the 1957 Edition of the Laws, the date of the patent in the United Kingdom; (d) in the case of a patent granted under the *Patents (Transitional Provisions) Act, 1958, the date specified in paragraph (b) or (c), as the case may be. (2) The date of a patent referred to in paragraph (a) or (d) of sub­ section (1). shall be entered in the register. ­ (3) The date of a patent referred to in paragraph (a) or (d) of sub­ section (1) shall be inserted in the patent. (No. 12 of 1959 as amended by G.N. No. 185 of 1964 and S.l. No. 175 of 1965) Extent, effect and fonn of patent 28. (1) Subject to the provisions of this Act, a patent shall have the same effect against the State as it has against a subject. (2) A patent shall be in such form as may be prescribed. (3) A patent shall be granted for one invention only, but it shall not be competent for any person in an action or other proceeding to take any objection to a patent on the ground that it has been granted for more than one invention. (4) The effect of a patent shall be to grant to the patentee, subject to the provisions of this Act and the conditions of the patent, full power, sole privilege and authority by himself, his agents and licensees during the term of the patent to make, use, exercise and vend the invention within Zambia in such a manner as to him seems meet, so that he shall have and enjoy the whole profit and advantage accruing by reason of the invention during the term of the patent. (As amended by G.N. No. 185 of 1964 and S.l. No. 175 of 1965) *Repealed by Act No. 15 of 1965.