The standard date and time - WWV
http://www.nist.gov/pml/div688/grp40/wwv.cfm
There's also WWVH in Hawaii -
http://tf.nist.gov/stations/wwvh.htm
There are also internet feeds for standard date and time -
http://tf.nist.gov/tf-cgi/servers.cgi
This is likely where your internet-connected devices are getting the data and time. There may be a menu option on devices that allows you to choose a date and time server by IP address. If not, Vizio likely has their own time server that echoes the time from one of the NIST sources.