[time-nuts] How do US TV stations disseminate time to DTV converter boxes?

[Greg Burnett]

How do US TV stations disseminate time to DTV converter boxes? ...And is 
this time derived from GPS data, or???

The question comes up tonight because, for some reason in my geographical 
area, the time indicated in the TV Guides of all DTV converter boxes is 1 
hour behind. We see the same symptom in at least two separate cities, 
separated by 70 miles - and regardless of which TV channel we select. We are 
seeing the same symptom on several different brands of DTV boxes. This 
symptom just began this afternoon or evening.

Any comments or information?

Greg

P.S. Side note: WWVB has been off the air many times in the last few weeks. 
They're currently off the air.