Why some sites show domain age and some don't? For example if I check my 2 domains in any tool that shows domain age, one shows the date and other one not. What is the deal here?
goggle is not using public tools to check the age of a domain, they use their own tools, their bots will recognize and credit your websites for the ages, so there is nothing to be worried about.
Are you sure that I have nothing to worry about? Why for example Alexa also does not show domain age for some domains? Is there a way to correct this?
1. google has access to Whois . So google perfectly knows your domain age 2. google does not use external tools in order to know domain age 3. Last but not least, domain age does not matter for ranking (SERPs). Instead of it, the real age of the page or, more exactly, its content is relevant for ranking. The age of your content depends on when google bot visited the content the first time. That may be quite different from the domain age, for instance if the domain had several owners or contents.
Google (like Yahoo! and most of the bigger search engines) is a Domain Registrar just like Godaddy or Network Solutions where you would go to register domains. Google doesn't sell domains. They are a registrar for just this reason, so that they can have access to registration information and history for reviewing sites for penalties and bans. They don't need to use public tools to get to your information info and the registration history of your domain. They have access to it (even info on privately registered domains) because they are themselves a registrar.