title: Why are there duplicate files when extracting tar.gz archive
body: <p>I have a strange problem with tar.gz archives that I do not understand.</p>
  
  <p>I create the archive on a linux server with <code>tar -czf</code></p>
  
  <p>When I extract them on a windows machine using <code>7z x</code>, I always get notifications that some (not all) files already exist. (They are extracted to an empty directory.) </p>
  
  <p>The files it wants to replace have todays date, the ones already there have the original (modified on) date they had on the server. </p>
  
  <p>Since I want to preserve the original timestamps I can use the <code>-aos</code> option for 7z, but I would like to understand why this is happening and make sure that I have an identical mirror of the files on the server after unpacking locally.</p>