title: Set DATE_TRUNC week date to Saturday instead of Monday
body: <p>I have daily data that I wanted to aggregate to weekly. The date_trunc function sets the default day to Monday. I wanted to start the week date to Saturday.</p>
  
  <p>I tried the following but didn't work:</p>
  
  <pre><code>DATE_TRUNC('week',(ds + interval '1 day')) - interval '1 day' AS _week
  </code></pre>
  
  <p>This is the DATE_TRUNC function that worked fine but starts Monday:</p>
  
  <pre><code>DATE_TRUNC('week', DATE(ds))
  </code></pre>
  
  <p>This is the error I got when using the first code:</p>
  
  <pre><code>(SYNTAX_ERROR) line 32:67: mismatched input 'AS'. Expecting: '%', '*', '+', '-', '.', '/', 'AT', '[', '||', &lt;expression&gt;
  </code></pre>