If you use the analog, composite signal to some DVD recorder you usually can turn on the time stamp and the DVD recorder will record it.
On the PC there are ways to add the timestamp but as you can set the time on the recorder any decent lawyer can dispute the time stamp.
My background includes the design of CCTV recorders and timestamps are fairly worthless as "proof." So be sure to get your lawyer to chat about ways to vet the date and time. Usually you want some of the video to pan over another source of the date/time such as a public time piece (clock tower or such) and more.
Some folk want to debate this but those that do tend to have not run into the lawyer that tore up the date/time stamp proof in court.
In closing, if you must use a PC, you can try one of those many Video capture devices.