title: Get timestamp difference using Ant
body: <p>I need to calculate time difference using Ant.<br>
  Basically it has 2 variables. One is assigned the current time, and the other one has a different time. I need to get the time difference using Ant. Something like below. If anyone have code please reply.</p>
  
  <pre><code>variable a = current time;
  variable b = different time
  echo (a - b) ;
  </code></pre>