title: What is the difference between when the timestamp is in the column and when it is in the index?
body: <p>Assuming that you are learning time series data with GBM, what is the difference between when the timestamp is in the column and when it is in the index?</p>
  <p>Does it change the accuracy? Or when using a timestamp as an index, doesn't it function as a feature of the model?</p>
  <p>case1) when the timestamp is in the column</p>
  <p><a href="https://i.stack.imgur.com/UCjb5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UCjb5.png" alt="enter image description here" /></a></p>
  <p>case2) when timestamp is in the index</p>
  <p><a href="https://i.stack.imgur.com/ruJZv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ruJZv.png" alt="enter image description here" /></a></p>