title: Postgres: Update date and retain time from timestamp
body: <p>I have a field1 with <code>timestamp</code>, <code>datatype</code> and values format is <code>2016-02-23 12:01:30</code>.</p>
  
  <p>I'm running the query:</p>
  
  <pre><code>UPDATE &lt;table&gt; set field1 = '2015-12-31'::timestamp::date where .....
  </code></pre>
  
  <p>The output changes to:</p>
  
  <pre><code>  2015-12-31 00:00:00
  </code></pre>
  
  <p>It converts the time to all zero's.  How to change the date and retain the timestamp?</p>