title: PHP convert week number and year back to Carbon?
body: <p>I'm using format W-Y  for weeknumber &amp; year.</p>
  
  <p>e.g. the final week of 2018 would be represented as <code>'52-2018'</code>.</p>
  
  <p>But I can't get Carbon or DateTime to convert it back.</p>
  
  <pre><code>&gt;&gt;&gt; Carbon::createFromFormat('W-Y', '01-2018')
  
  InvalidArgumentException with message 'The format separator does not match
  The separation symbol could not be found
  Trailing data'
  </code></pre>