These Regulations amend the definition of “exit day” in section 20(1) of the European Union (Withdrawal) Act 2018 to 22 May 2019 at 11.00 p.m., if the negotiated withdrawal agreement has been approved by the House of Commons, or to 12 April 2019 at 11.00 p.m., if the negotiated withdrawal agreement has not been approved by the House of Commons and consequently amend section 20(2) of the 2018 Act. “Exit day” is the day by reference to which provisions of the 2018 Act, including the repeal of the European Communities Act 1972, and a wide range of related primary and secondary legislation, take effect or come into force.
Also see EU Exit SI tracker