The age of the domain is built up of how long the content has been actually on the web, how long the site has been in promotion,and even the last time content was updated.
So the age of the domain name plays a vital role in ranking........
If you are having an old domain name...........that adds more credibility to your search engine rankings..
especially Google gives more importance to domain age...........
So using this site WhoisXY.com/ , you can gather the information of the domain name creator and owner of the domain name also it displays the information of the domain name that is when is expired & created........its a easy way to find the age of domain name.........