title: NLTK for Named Entity Recognition
body: <p>I am trying to use NLTK toolkit to get extract place, date and time from text messages. I just installed the toolkit on my machine and I wrote this quick snippet to test it out:</p>
  
  <pre><code>sentence = "Let's meet tomorrow at 9 pm";
  tokens = nltk.word_tokenize(sentence)
  pos_tags = nltk.pos_tag(tokens)
  print nltk.ne_chunk(pos_tags, binary=True)
  </code></pre>
  
  <p>I was assuming that it will identify the date (tomorrow) and time (9 pm). But, surprisingly it failed to recognize that. I get the following result when I run my above code:</p>
  
  <pre><code>(S (GPE Let/NNP) 's/POS meet/NN tomorrow/NN at/IN 9/CD pm/NN)
  </code></pre>
  
  <p>Can someone help me understand if I am missing something or NLTK is just not mature enough to tag time and date properly. Thanks!</p>