title: Subtracting row values in DAX ; Power BI
body: <p>If I have data of this sort:
  <a href="https://i.stack.imgur.com/3Pnyh.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3Pnyh.jpg" alt="enter image description here"></a></p>
  
  <p>I'd like to calculate the time difference between a value in Bi and Bi+1, in PowerBI. That is, in a new a column, in the Query Editor (so writing in M), I want to have:</p>
  
  <p>C3 = B3-B2</p>
  
  <p>C4 = B4 - B3</p>
  
  <p>and so on.</p>
  
  <p>Do you know how to achieve this in PowerBI?</p>