There is:

61.35(a)(2)(iii) Date of birth, which shows the applicant meets or will meet the age requirements of this part for the certificate sought before the expiration date of the airman knowledge test report


Edit: On the other discussion with taking it early versus late, I am the opposite end of the spectrum. I wait until the check ride is in sight, approximately 10 lessons left, to take the written. Start studying for it around the halfway point. I have two reasons for this belief:

1) They can use the written exam to help prepare them for the oral exam. It covers much of the same content and I like to have that fresh in their head.

2) Optimally they should take the written first and then study equally as hard for the oral as they had to to take the written in the first place. Realistically, they probably won't. So this method forces them to study, so to speak.