title: Pandas timestamp to and from json
body: <p>Objects cannot be serialised to json so therefore need to be converted or parsed through a custom JsonEncoder class.</p>
  
  <p>pandas Dataframe has a number of methods, like <code>from_records</code> to read json data. Yet when you read that json data back it is returned as int64 instead of timestamp.</p>
  
  <p>There are many ways to skin a cat in pandas. What is the best way to preserve data structures when reading and writing json?</p>