title: Update single column in 2-D array
body: <p>I have a 2-dimensional array like below. The first column is a date and I would like to store it as a number of milliseconds using the <code>getTime()</code> function so that I can use it for date comparisons later. Is there an easy way to update a single column in a 2-d array? The original array could have multiple columns.
  I'm trying to update the date column here which is the first column. So for example, instead of <code>Mon Aug 10 00:00:00 GMT-05:00 2020</code>, it should have value returned by <code>getTime()</code> on the date object represented by <code>Mon Aug 10 00:00:00 GMT-05:00 2020</code></p>
  <pre><code> [[Mon Aug 10 00:00:00 GMT-05:00 2020, 7.7107286E7, A-Plus Restoration], 
  [Sun Feb 09 00:00:00 GMT-06:00 2020, 7.1324511E7, Kwik-E-Mart Industries], 
  [Sun Mar 08 00:00:00 GMT-06:00 2020, 7.5233927E7, Jacob Tannenbaum], 
  [Wed Mar 25 23:00:00 GMT-06:00 2020, 7.7678662E7, Music Depot]]
  </code></pre>