There is quite a bit of information available online, at your local school district and through support groups which may be able to help you learn more about your son's developmental profile. It is hard to say if a child has Aspergers syndrome based on one very unique talent, memorizing the calendar. Usually, determinations are made of Aspergers based on a group of behaviors vs. one unique behavior.
Please consider seeking more information from the professionals who are working with your son.
Louise Masin Sattler, NCSP
Nationally Certified School Psychologist