It depends on your objective in enlisting. If your goal is to accrue time toward retirement benefits, you must be able to complete 20 combined years of service by age 60. The PS applicant 35 years of age or older has prior qualifying service which can then be subtracted from their current age, bringing their enlistment age to less than "35," and the applicant can qualify for retired pay by age 60.
Example: PS applicant is 47 years old with 13 years of qualifying service, which brings the applicant to an enlistment age of "34." If the applicant only had 12 years of qualifying service, then the enlistment age would be "35" and the applicant would not be qualified.
If retirement benefits are not your objective in joining, your maximum age will depend on your specific service history. No two situations are alike. Please speak to a recruiter to discuss how your age affects your enlistment.