title: Date subtraction in bash
body: <p>I want to get successive differences of dates shown sample below. How do I convert each of these dates into epoch seconds? </p>
  
  <pre><code>7/21/17 6:39:12:167 GMT
  7/21/17 6:39:12:168 GMT
  7/21/17 6:39:12:168 GMT
  7/21/17 6:39:12:205 GMT
  7/21/17 6:39:12:206 GMT
  7/21/17 6:39:12:206 GMT
  </code></pre>
  
  <p>Once each line gets converted into epoch seconds, I can simply run another script to get successive differentials of each. Thanks.</p>