Merge date and time columns
<p>Currently I have 2 columns one that holds dates and the other holds the time (24hr text version). </p>

<p>Example:</p>

<pre><code>a_dt          a_time_text
01-Jan-15     0224
31-Mar-15     0317
15-Sep-15     2010
</code></pre>

<p>How do I create a new column that hold the date and time, like this:</p>

<pre><code>a_dt_tm
01-Jan-15 02:24
31-Mar-15 03:17
15-Sep-15 20:10
</code></pre>

<p>Or any other way so that I can find the difference in date/time between another variable.</p>