When the fall TV season kicks off and Facebook users around the country are catching up on their favorite programs during the daily commute, Nielsen will be watching. A new partnership between the social network and Nielsen will allow Facebook to send viewer details, like age and gender, to the TV-stat-crunching company, in an effort to help advertisers learn about what shows folks are watching online. Appointment viewing has gone the way of bunny ears and “Must See TV,” and Nielsen can no longer rely on its now-antiquated ways of measuring television ratings. Instead, the company must tap into data providers like Facebook. The move dates back to October, when Nielsen revealed its new software development kit for content providers that can integrate Nielsen’s technology into browser-based video players and branded apps.