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”.