title: Periodicity inside time series: I have the period itself, how can I know where the periodicity started?
body: <p>I have a time-series that contains a hidden periodicity in the data.
  I already found the period itself (e.g., 60 minutes, 100 minutes).
  How can I find the specific sequence that has the periodicity? note that the periodicity can even start in the middle of the time series.</p>
  
  <p>What can I do about it?</p>