title: Power BI Power Query: Adding Custom Column is Changing Date Format
body: <p>I have an Azure Databricks data source, and I am experiencing the strangest behavior I have ever seen. I have a datetime field that has milliseconds that I need to retain.</p>
  <p><a href="https://i.stack.imgur.com/r9HoW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/r9HoW.png" alt="enter image description here" /></a></p>
  <p>I am able to parse this out to get just the milliseconds, or create a text-friendly key field, but as soon as I add any Custom Column step, the date gets reformatted and drops the milliseconds, which then ruins my other calculations.</p>
  <p><a href="https://i.stack.imgur.com/cDkzd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cDkzd.png" alt="enter image description here" /></a></p>
  <p>The datetime column remains Text data type.  The custom column is not referencing my datetime--it's a completely unrelated calculation.  It's as if, during calculation of a new field, it creates a shallow copy that then re-detects the metadata and tries to be smart about datetimes.</p>
  <p>I have no idea how to stop this.  I have disabled the following Options:</p>
  <p><a href="https://i.stack.imgur.com/SYbM2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SYbM2.png" alt="enter image description here" /></a></p>
  <p>This is literally blocking me from doing duration analysis on events.  Has anyone encountered this before?</p>