title: SOQL query WHERE Date = 30_days_ago?
body: <p>How do I make a SOQL query like this?</p>
  
  <pre><code>SELECT id FROM Account WHERE LastActivityDate = 30_DAYS_AGO
  </code></pre>
  
  <p>This produces an error:</p>
  
  <pre><code>MALFORMED_QUERY: 
  Account WHERE LastActivityDate = 30_DAYS_AGO
                        ^
  </code></pre>