Section 16 of the Principal Act is repealed and the following section is substituted:

16.     Imprisonment

(1)  In this section,

sentence of imprisonment means –

(a) a sentence of imprisonment imposed on a child by a children's court; or

(b) a sentence of imprisonment imposed on a person by a court of summary jurisdiction for an offence that the person committed as a child.

(2)  A sentence of imprisonment in force immediately before the commencement day is taken to be a sentence of detention imposed under the Youth Justice Act 1997 and has effect until the first of the following occurs:

(a) the sentence is served;

(b) the period of 2 years commencing on the commencement day expires.