Parliamentary Voting System and Constituencies Bill

Surely the logic of the hon. Lady's position is to say that everyone who was born before 6 May 1997 should be entitled to vote in the referendum, if that is to be relevant on the day of the now-fixed election in May 2015. Why does she not have that date in mind? Is it the absurdity of people being entitled to vote in the referendum at age 14 years and eight months that dissuades her from going down that route?