title: Detecting missing timestamp
body: <p>I have following dataframe having a timestamp and value. Timestamp increases by 5 seconds and notice that there are missing records between 23:02:02 &amp; 23:06:32. </p>
  
  <p>Is there a simple way to detect if there are missing records between timestamps?</p>
  
  <pre><code>timestamp   value
  23:01:27    2915
  23:01:32    2916
  23:01:37    2919
  23:01:42    2924
  23:01:47    2926
  23:01:52    2928
  23:01:57    2933
  23:02:02    2937 # &lt;- missing timestamp
  23:06:32    3102 # &lt;- between these lines
  23:06:37    3109
  23:06:42    3114
  23:06:47    3122
  23:06:52    3126
  23:06:57    3129
  </code></pre>