title: How to change only the date portion of a DateTime, while keeping the time portion?
body: <p>I use many DateTime in my code. I want to change those DateTimes to my specific date and keep
  time.</p>
  
  <pre class="lang-none prettyprint-override"><code>1. "2012/02/02 06:00:00" =&gt; "2015/12/12 : 06:00:00"
  2. "2013/02/02 12:00:00" =&gt; "2015/12/12 : 12:00:00"
  </code></pre>
  
  <p>I use this style to change, but it seem not the good way and I want to ask have any way to achieve this task.</p>
  
  <pre><code>DateTime newDateTime = new DateTime(2015,12,12,oldDateTime.Hour,oldDateTime.Minute,0);
  </code></pre>