How to add a time stamp using ffmpeg to a screenshot capture of a video
Use

ffmpeg -start_at_zero -copyts -ss 00:00:14.435 -i input.mp4
    -vf "drawtext=fontfile=/path/to/Arial.ttf:
          fontsize=45:fontcolor=yellow:box=1:boxcolor=black:x=(W-tw)/2:y=H-th-10:
          text='Time\: %{pts\:hms}'"
    -vframes 1 output.png