title: equivalent date from GNU to solaris
body: <p>In <code>GNU</code> with the command date I can do it:</p>
  
  <pre><code>date -d "+4 day"
  
  
  datei=20130101
  i=5
  date -d "$datei +$i day"
  </code></pre>
  
  <p>But i like know:</p>
  
  <p>how can i do it in Solaris? </p>
  
  <p>with the date command</p>