(1) Section 83 of the Principal Act is hereby amended by the insertion after subsection (4) of the following subsections:
"(5) For the purposes of this Chapter -
'entry into insurance' means, in relation to any person, whichever occurs first -
(a) the date on which he first becomes an insured person by virtue of section 5 (1), except where he becomes an insured person by virtue of paragraph (b) of subsection (1) of the said section 5 only, or
(b) the date on which he first becomes an insured person by virtue of section 17A,
and that that date shall be regarded as the date of entry into insurance for the purposes of paragraphs (a) and (c) of section 84(1).
(6) Notwithstanding subsection (5), regulations may provide that the date on which a person first becomes an employed person or a self-employed person, insurable for old age pension or retirement pension purposes under the legislation of another Member State of the European Communities, or under the legislation of any other State