Section 20: Interpretation
Subsection (1) defines certain terms used throughout the Act.
	In the definition of enactment, paragraph (a) does not cross-refer to the definition of subordinate legislation in the Interpretation Act 1978 as the Act amends that definition to take account of retained direct EU legislation. Paragraph (h) provides that retained direct EU legislation is included within the definition of enactment save for in sections 2 (as retained direct EU legislation is not saved by section 2) and 7 (which makes reference to enactments before exit day).
	Subsection (1) also defines exit day as 11.00pm on 29 March 2019. This is in line with the calculation of time in EU law, as well as the EU’s negotiating directives, which indicate that the UK will leave the EU at 00.00 on 30 March Brussels time, corresponding to 11.00pm on 29 March UK time.
	Subsection (2) makes further provision about the meaning of references to exit day. References in the Act to before, after or on exit day, or to beginning with exit day, are to be read as references to before, after or at 11.00pm on 29 March 2019 or (as the case may be) to beginning with 11.00pm on that day.
	Subsections (3) and (4) provide that if the date and time at which the EU Treaties cease to apply to the UK is not the date and time specified in subsection (1), a minister may make regulations to amend the definition of exit day in this Act to ensure that they are aligned. A change in the date is possible under Article 50(3) of the TEU. Regulations made under subsection (4) would be subject to the affirmative procedure (see Schedule 7, paragraph 14).
	Subsection (6) provides that references in the Act to things which continue to be domestic law, include things which would have continued to exist regardless of the saving in section 2. This makes clear that it is not necessary to consider whether an enactment might have been subject to implied repeal as a result of repeal of the ECA, in order to bring it within the ambit of section 2 and therefore the definition of "retained EU law".
	Subsection (7) provides that references to the retained EU law brought in by section 4 include any modifications which may be made to that law from time to time.
	Subsection (8) is self-explanatory.
	Subsection (9) provides that any reference in the Act to the former Article 34(2)(c) of the TEU (which concerned decisions in the field of police and judicial cooperation in criminal matters) is a reference to that Article as it applied before the Lisbon Treaty. It is necessary to include these references in the Act to ensure that it accurately reflects the legal basis for these measures.
	Subsection (10) provides that references in the Act to certain provisions of the TEU and TFEU include references to those provisions as they apply to the Euratom Treaty.