title: ERROR: operator does not exist: timestamp without time zone + integer
body: <p>i am adding nthmonth (2) in my postgresql function , but at the time of execution it showing error "ERROR:  operator does not exist: timestamp without time zone + integer"
  HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
  QUERY:  SELECT pi_date  +   nthMonth || ' month ' :: INTERVAL</p>
  
  <pre><code>DECLARE
  beginMonth  timestamp;
  pi_date     timestamp := to_timestamp('14-Jan-2016 01:50 AM,'DD-MON-YYYY HH:MI AM);
  &gt; beginMonth := pi_date  +   nthMonth || ' month ' :: INTERVAL;
  </code></pre>