title: GPG error: http://archive.debian.org lenny/updates Release: The following signatures were invalid: KEYEXPIRED 1356982504
body: <p>I am getting following error while update my source lists</p>
  
  <pre><code>$ sudo apt-get update
  
  Reading package lists... Done
  
  W: GPG error: http://archive.debian.org lenny/updates Release: The following signatures were invalid: KEYEXPIRED 1356982504
  
  W: You may want to run apt-get update to correct these problems
  </code></pre>
  
  <p><strong>How to resolve this issue?</strong></p>