Sometimes it&#x27;s useful to be able to prove a file was created &#x2F;before&#x2F; a given time.<p>For example, if you download a signed executable, but the signing certificate expired a while ago, does that mean you don&#x27;t trust the executable? If you don&#x27;t trust it, every executable would eventually break when the signing certificate went out of date. The solution is to require a cryptographic timestamp proving the executable was generated at a time when the code signing certificate was valid.<p>That&#x27;s how you can download Java applets that were published and signed in 2005 and still know the signature is valid. Not that many people are using that technology these days!