title: Pandas check time series continuity
body: <p>I have a DataFrame with monthly index. I want to examine whether the time index is continuous on the monthly frequency, and, if possible, spots where it becomes discontinuous e.g. has certain "gap months" between two months that are adjacent in its index.</p>
  
  <p>Example: the following time series data</p>
  
  <pre><code>1964-07-31    100.00
  1964-08-31     98.81
  1964-09-30    101.21
  1964-11-30    101.42
  1964-12-31    101.45
  1965-03-31     91.49
  1965-04-30     90.33
  1965-05-31     85.23
  1965-06-30     86.10
  1965-08-31     84.26
  </code></pre>
  
  <p>misses 1964/10, 1965/[1,2,7]. </p>