ios 7 typography on labels and UIFont

ios 7 typography on labels and UIFont

I have the following code:
UILabel *registerLabel = [ [UILabel alloc ] initWithFrame:CGRectMake(20.0,
90.0, [self screenWidth], 43.0) ];
registerLabel.textAlignment = NSTextAlignmentLeft;
registerLabel.textColor = [UIColor whiteColor];
registerLabel.backgroundColor = [UIColor blackColor];
registerLabel.font = [UIFont fontWithName:@"Helvetica Neue" size:(20.0)];
//registerLabel.adjustsFontSizeToFitWidth = YES;
registerLabel.text = @"Register";
But I see in some of the ios 7 demo apps (like calendar) the font is large
but much thinner. I tried using Helevetica Neue Light but that doesn't
work. Is there a way to make the font thinner or what font are they using?