MacOS – Numbers version 5.3(5989). How to Calculate Duration by comparing two cells formatted as datetime

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Column A has been formatted in the “datetime” format. Date and time from my glucose meter were entered into Column A and displays as in the default option I selected. Column D is the glucose readings and is not an issue in this question. (Datetime format displays as “1/5/2019 1805”). Also Column A has been sorted in ascending order and verified.
Column B is formatted as “duration”.
What is the function (formula) to compute the interval between successive dates & times in Column A?
Every attempt I have made results in “number was expected”.

Best Answer

You just need to subtract the later from the former.

ie: B2-B1

Example in the image