title: How to calculate number of days in last 3 months
body: <p>How we can calculate, number of days in last 3 months?</p>
  
  <p>i.e. - today is <code>11-11-2013</code></p>
  
  <p>I want to calculate total number of days from <code>1st September</code> to <code>today</code>; i.e. 72 days.</p>
  
  <p>1st November wil change automatically.</p>