title: How to set the period of a periodic task in Firebase JobDispatcher?
body: <p>I've read every available official docs (which is surprisingly not a lot) and all I could get for periodic tasks is this code</p>
  
  <pre><code>            .setRecurring(true)
              // start between 0 and 60 seconds from now
              .setTrigger(Trigger.executionWindow(0, 60))
  </code></pre>
  
  <p>I know that <code>.setRecurring</code>makes the job periodic and that the <code>trigger</code> makes it start in a 60 seconds interval but what about the second time it's executed ? does this mean that the 2nd time would be also executed 60 seconds starting from the 1st one ?</p>
  
  <p>This can't be true because even taking in consideration the optimisation in the background activities and how services run a little later than they're supposed to, programming 60 seconds period while the job runs about 5/10/20 minutes later is too much of a difference. The official docs say that the difference is seconds and maybe a few minutes not over 20 mins.</p>
  
  <p><strong>Basically, my question is does this          <code>.setTrigger(Trigger.executionWindow(0, 60))</code> really mean that the period is 60 seconds or am I gettin this wrong ?</strong></p>