The Eighteenth Amendment of the Constitution of India, officially known as The Constitution (Eighteenth Amendment) Act, 1966, Parliament may by law
(a) form a new State by separation of territory from any State or by uniting two or more States or parts of States or by uniting any territory to a part of any State;
(b) increase the area of any State;
(c) diminish the area of any State;
(d) alter the boundaries of any State;
(e) alter the name of any State:
Hence, this amendment reorganised Punjab into Punjab, Haryana and UT of Chandigarh.