General Clauses Act, 1897
5. Coming into operation of enactment
15[(1) Where any Central Act is not expressed to come into operation on particular day, then it shall come into operation on the day on which it receives the assent-
(a) in the case of a Central Act made before the commencement of the Constitution, of the Governor-General, and
(b) in the case of an Act of Parliament, of the President].
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(3) Unless the contrary is expressed, a 13[Central Act] or Regulation shall be construed as coming into operation immediately on the expiration of the day preceding its commencement.