Section 54 of the Principal Act is amended as follows:

(a) by omitting from subsection (2) "period" and substituting "relevant period" ;

(b) by omitting from subsection (2) ", whichever is applicable," ;

(c) by omitting from subsection (2A)(b) "the authority" and substituting "the planning authority" ;

(d) by omitting from subsection (2A) "period" first occurring and substituting "relevant period" .