The Age of your website domain name is domain name age.Yes Domain Name age is very important in Page Rank.If your Domain name age is high .It will get high rank in GOOGLE and Other Search engines.Domain name age calculated by Domain name creation date and expiration date.So domain name age plays a vital role in SEO.You can check Domain name age using the site
www.whoisxy.com it shows Domain name creation and expiration details,domain name owner details etc.