Section 21A of the Principal Act is amended as follows:(a) by omitting from paragraph (a) "January" and substituting "July" ;(b) by omitting from paragraph (a) "31 March" and substituting "30 September" ;(c) by omitting from paragraph (b) "April" and substituting "October" ;(d) by omitting from paragraph (b) "30 June" and substituting "31 December" ;(e) by omitting from paragraph (c) "July" and substituting "January" ;(f) by omitting from paragraph (c) "30 September" and substituting "31 March" ;(g) by omitting from paragraph (d) "October" and substituting "April" ;(h) by omitting from paragraph (d) "31 December" and substituting "30 June" .