the legal units of measurement within the meaning of this Directive which must be used for expressing quantities shall be: (a) those listed in Chapter I of the Annex; (b) those listed in Chapter II of the Annex, until a date to be fixed by the Member States; this date may not be later than 31 December 1985; (c) those listed in Chapter III of the Annex only in those Member States where they were authorized on 21 April 1973 and until a date to be fixed by those Member States; this date may not be later than a date to be set by the Council before 31 December 1989 on the basis of Article 100 of the Treaty