Hi
VP itself, doesn't have a way of adding a clock to a video. However you could quite easily download a working digital clock display from UTube or even film a digital clock or stopwatch for a time similar to your video.
This clip can then be placed on the overlay track and reduced in size using the SCALE effect and moved using the POSITION effect so it appears in the frame where you want it to.
If only the digits are required then, providing the the background colour of the figures is a single shade, you can use the GREEN SCREEN effect to render this transparent.
Any exported clips made from this video would then contain the "time stamp"
Nat