title: How to select observations of df using datetime index atributes in Pandas?
body: <p>Given a df of this kind, where we have DateTime Index:</p>
  
  <pre><code>DateTime               A                           
  2007-08-07 18:00:00    1
  2007-08-08 00:00:00    2
  2007-08-08 06:00:00    3
  2007-08-08 12:00:00    4
  2007-08-08 18:00:00    5
  2007-11-02 18:00:00    6
  2007-11-03 00:00:00    7
  2007-11-03 06:00:00    8
  2007-11-03 12:00:00    9
  2007-11-03 18:00:00   10
  </code></pre>
  
  <p>I would like to subset observations using the attributes of the index, like:</p>
  
  <ul>
  <li>First business day of the month</li>
  <li>Last business day of the month</li>
  <li>First Friday of the month 'WOM-1FRI'</li>
  <li>Third Friday of the month 'WOM-3FRI'</li>
  </ul>
  
  <p>I'm specifically interested to know if this can be done using something like:</p>
  
  <pre><code>df.loc[(df['A'] &lt; 5) &amp; (df.index == 'WOM-3FRI'), 'Signal'] = 1
  </code></pre>
  
  <p>Thanks</p>