Many SEO experts believe that the date a domain was originally registered is a weight factor with the major Search Engines. There is quite a bit of evidence to support this theory.
PS: The length of time that a domain is renewed or registered for is also an SEO factor. If you register domains, always go for at least two years. I tend to do three to five years now on new domains I pick up. The conventional wisdom being that doorway pages or churn and burn spam pages are almost always registered for only one year. Businesses who purchase a multi year registration are demonstrating an intent to build a domain that has value.