title: How to get min date from Laravel collection
body: <p>I have collection <code>promotions</code> and each promotion has many <code>exceptions</code>:</p>
  
  <pre><code>foreach ($promotions as $p) {
      $t = $p-&gt;exceptions()
              -&gt;where('sunday','on')
              -&gt;whereDate('start','&lt;=', $c_date)
              -&gt;whereDate('end','&gt;=', $c_date)
              -&gt;get()
              -&gt;sortBy('promotion_id');
  
      echo $t-&gt;min('start'). ' from: '.$t-&gt;min('start_time') .' ';
      echo $t-&gt;max('end') . ' to: '.$t-&gt;max('end_time').'&lt;/br&gt;';
  }
  </code></pre>
  
  <p>Because a promotion has many exceptions I need to know for each promotion min date and max date.</p>
  
  <p>The code above works good but its uses 'start' as the string not as date and results are not valid.</p>
  
  <p>How I can get min date and max date from the collection.</p>