I guess you're talking about the MPEG 2 TDT? This is a standard MPEG 2 transport stream table. You'd need a tuner to tune the signal and then some kind of software or firmware to parse the transport stream and pull out the detail that you need. Seems like quite an involved way to get the time. What kind of device are we talking about?
Surely a GPS receiver would be easier and tell you to nano-second accuracy. Some GPS receivers have a serial connection and I remember coding some API to use it once (in ye olde days circa 2000). (Geez, some probably are USB or wifi these days). It's in the 300 baud rate ephemeris data. You can get the time out of it I think only locked onto a single sat.