title: Vim strftime calculations
body: <p>I have a very simple ToDo file which looks like this :</p>
  
  <pre><code>130821 Go to the dentist
  130824 Ask a question to StackOverflow
  130827 Read the Vim Manual
  130905 Stop reading the Vim Manual
  </code></pre>
  
  <p>I would like to calculate - each time I open the file - the number of days remaining until the different due dates (today is the 22nd of August 2013, i.e. 130822, in Paris), thus obtaining something like : </p>
  
  <pre><code>130821 -1 Go to the dentist
  130824 2 Ask a question to StackOverflow
  130827 5 Read the Vim Manual
  130905 14 Stop reading the Vim Manual
  </code></pre>
  
  <p>but I do not know how to achieve that (and I do not know if it is reasonably possible : cf. glts'comment)</p>
  
  <p>Your help would be appreciated.</p>