The Whois Data Reminder Policy (WDRP) is a consensus policy adopted by the Internet Corporation for Assigned Names and Numbers (ICANN), which requires domain name registrants to review the contact information associated with their domain names and make corrections when necessary.  As a part of this, domain name registrars are required to formally remind their customers once a year to review and update their contact information.  For detailed information about the adoption of the WDRP, see http://www.icann.org/registrars/wdrp.htm.