The number of times a visitor returned to a website is calculated based on the lifetime of the Yahoo! Web Analytics cookie stored in the visitor’s browser. The lifetime of the Yahoo! Web Analytics cookie can be up to one year since the last visit.

The first time a visitor comes to your website, Yahoo! Web Analytics sets a one-year, first-party, persistent cookie in their browser that includes a unique visitor ID number. During the first visit, Yahoo! Web Analytics identifies them as a first time visitor. On subsequent visits, Yahoo! Web Analytics resets the cookie life to one year beyond the date of the visit, and identifies them as a returning visitor for the duration of that visit. If the cookie is reset once for a visitor, then that visitor had two visits; if the cookie is reset twice, then the visitor had three visits, etc.

If Yahoo! Web Analytics is unable to set a cookie, then it will identify the visitor as a first time visitor.