Google prompts you for your age when you set up an account on Gmail, or any other Google service, to comply with local and international law. You must be 13 or older to create a Google account in most countries, including the United States. If you have previously entered an incorrect birth date and are trying again with a new date, an error message could mean your browser still has the older entry stored in its cache.

Clearing Browser Cache and Cookies

If you are seeing an error message when entering a birthday more than 13 years ago, try clearing your browser's cache and cookies. In Internet Explorer, open the Tools menu (a cog icon) then choose "Internet Options" and "Delete." In Mozilla Firefox, choose "Firefox | Options | Options." You can clear the cache from the Network tab under Advanced and cookies from the Privacy tab. In Google Chrome, choose "Tools" and then "Clear Browsing Data" to access the relevant dialog box.