To find the difference between 2 datetime with milliseconds

End time - January 12th 2019, 00:04:23.220, Plan time - January 11th 2019, 23:49:54.042
How to find difference between 2 dates plan time vs end time, which has milliseconds component too either using power BI or Power query please.

The quickest solution would be to just convert the columns for End Time & Plan Time to Date/Time and Format of (HH:mm:ss). Then you could do a calculated column for the difference. It would be as easy as Plan Time- End Time.