title: Redshift - Convert epoch string to timestamp
body: <p>I have got a table with 2 columns epoch_start and epoch_end.
  I want to find the difference in days of these 2 epochs.<br>
  The problem i am facing is that the above columns are character varying(5000) type.
  The query im running is     </p>
  
  <blockquote>
    <p>select datediff(day,'1459762341','1450762341') as numdays;</p>
  </blockquote>
  
  <p>The error i get is      </p>
  
  <blockquote>
    <p>ERROR:  invalid input syntax for type timestamp: "1459762341"</p>
  </blockquote>