title: Adding Days to defined date on XSLT
body: <p>im trying to add seven days from my defined day, 
  i've a defined date like this </p>
  
  <pre><code>//n1:Invoice/cbc:IssueDate
  </code></pre>
  
  <p>i m using date like this and it works</p>
  
  <pre><code>&lt;xsl:value-of select="//n1:Invoice/cbc:IssueDate" /&gt;
  </code></pre>
  
  <p>that turns me <code>20-01-2016</code>
  and i want to print seven days after this date like:</p>
  
  <pre><code>27-01-2016
  </code></pre>
  
  <p>any idea?</p>