Hi, It's pretty much well known that google values the age of a domain very highly. But I just wanted to ask a couple of questions about how the domain age is handled: If a 5 year old domain expires, and I register it, does it remain a 5 year old domain in google's eyes, or does it become a brand new domain again? If I buy a 5 year old domain from someone, therefore all the registration details change, does google keep recognising it as a 5 year old domain? Thank you in advance for any answers!
As far as I am concerned, Google recognizes the age of a domain by referring back to the first date the domain is accessible to public and the googlebot. So if the contents have been changing over time, or the domain has been moving from one person to another person, or even the registrar has been changed, Google doesn't judge the domain as a new domain. In short, an old domain is always an old domain, no matter what. Remember, there is a website that keeps almost all the histories of domains that have been around on the internet. You can go to archive.org to check it out.
if a domain expired and some one again registered then it's a fresh new domain as domain reg. date changed so google considers it as a new domain. Important is domain reg. date
I think we need to make a clear comparison between domain and website. A domain in simple terms means a 'registered name' whereas a website is what is inside a domain. So it is possible to have a domain without a website, for example a parked domain. But as I said, in Google's sight, an old domain is always an old domain no matter what happens to the domain over time. However, if someone purchases an old domain that has been known for a particular niche and been crawled by Google with particular keywords that are related to the website, but then the person changes the domain's niche into a completely new topic, then Google will consider it as a new website. Google therefore needs to re-index the website and look for some peculiar keywords that the new website is using. Let's put that aside. If you are planning to buy an old domain because you know the advantages of having an old domain that Google will treat differently from newly-born domains, you'd better buy the one that has already been known with the niche you are going to use. Otherwise, it is not worth spending the time looking for old domains for sale that you don't even know what they have been used for. My suggestion would be always referring back to archive.org whenever you want to know the history of an old domain.
At the moment I'm leaning towards this being the correct answer. I've checked a couple of domains which expired and were re-registered, and all whois sites show the new registered date rather than the original, so I'm assuming that's also what Google would use. Thanks to everyone for the replies.