title: InfluxDB - what's shard group duration
body: <p>I have created one year policy in InfluxDB and shard group duration was automatically set to 168h.</p>
  
  <p>This is how my retentions look like now:</p>
  
  <p><a href="https://i.stack.imgur.com/sB2Zo.png" rel="noreferrer"><img src="https://i.stack.imgur.com/sB2Zo.png" alt="Retentions"></a></p>
  
  <p>This is how my shards look like now:</p>
  
  <p><a href="https://i.stack.imgur.com/6ug4t.png" rel="noreferrer"><img src="https://i.stack.imgur.com/6ug4t.png" alt="Shards"></a></p>
  
  <p>What does it mean for my data that shard's end time is set one week ahead?</p>