[d4g4m]

TV is connected only to antenna and DISH.
In TV set up, choose language, [to get date/time] choose time zone and enter zip code, [and my question is- who is sending it? one entity or each channel separately] do a channel scan.
Date/time is auto set. There is no manual date/time enter.
The time appears in the top/middle of the channel info pop up box. This function does not work when I switch TV input from antenna to cable. DISH info is totally separate and different. I use antenna because all main channels are HD and DISH does not carry any sub-channels like MEtv, anntennatv, movies, THIS, GETtv, bounce, escape, or my local Sarasota news channel and a few other channels.
Seems that this is a question that no one can answer. I've written to a few stations, a few other web sites, even the fcc.gov No answer from anyone.
ADDITIONAL INFO
I used every imaginable words and phrases searching for info about TV date/time and found nothing. So, thanks to timgr for including the Wikipedia link.
According to Wikipedia, 'program and system information protocol' it is defined in ATSC standard A/65:2013 and A/69 Besides regular programming info, data is transmitted to include 'time' [required by the FCC] All PSIP is required to be sent by every digital TV station. All of the info and data is sent OTA, received by an antenna to the TV receiver and the date/time has nothing to do with the TV being or not being connected to the internet with a router/modem. So, since the TV is losing the correct date/time on every channel, I can only assume that there's a problem with the TV tuner or the date/time IC chip. And back to Vizio tech support.