title: making a calculation on a timestamp array
body: <p>It is easy to perform a calculation on a timestamp:</p>
  
  <pre><code>from datetime import datetime
  timestamp = 1456741175
  dt = datetime.fromtimestamp(timestamp)
  print(dt.day)
  # Week day number
  print(dt.weekday())
  print(dt.minute)
  print(dt.second)
  </code></pre>
  
  <p>But how about if my timestamp is an array, instead of a single value. For e.g:</p>
  
  <pre><code>timestamp = [1456741175, 1456741176, 1456741177, ....]
  </code></pre>
  
  <p>With a loop, it takes a lot of time as my array's length is more than 3 million. So, how can I perform the same calculation on an array of timestamps using a method that is simple and fast?</p>