You can add a comment and time stamp to your digital signature.
Time services allow you to add the time stamp. When you send drawing files over the Internet or work on collaborative projects, you can use a specific time server to obtain an accurate, consistent time stamp.
Several government operations (such as the National Institute of Standards and Technology, or the US Naval Observatory) and public systems (such as California Institute of Technology) offer accurate time values. You can also use your own server to create a time stamp.