title: Convert system timezone in mysql returning null
body: <p>I'm trying to convert mysql current timezone, to another one. But I'm getting Null as answer:</p>
  
  <pre><code>select *, CONVERT_TZ(NOW(),@@session.time_zone, 'America/Sao Paulo')
  from historical_prices;
  </code></pre>
  
  <p>This is my query.</p>
  
  <p>How can I fix this?</p>