I don't have issues with OTA, but there surely are issues on my TWC system (QAM). There appears only one physical channel that has the correct time; ch. 21. All the others are off anywhere from 20 minutes to several hours. One even sets the clock to 00:00.
I tried to see if there is a pattern to this. It appears certain channels will change the time as soon as the video appears. Other channels have no effect. It also appears that it depends on where the last time set was made. The channels that change the time don't always do so when returning from the other channels that have changed it again.
Hopefully some of that make sense.
A possible solution is for the user to skip around (so to speak) and when he finds a channel (station) that sets the time correctly, have a menu entry :Use this station for the time set" or something similar. Then the system would ignore all other stations. This is of course if a actual manual time set is not possible as I was told.