I certainly agree that the date functions make life a whole lot easier in certain areas but I don't agree that they are any more accurate when it comes to durations and spans of time. Here's a simple example of displaying the difference between two dates and times in the classic HHHH:MM:SS:mmm format and the classic decimal hours format. If there's a simpler or more performant method to do the same things using only date fuctions, I'd love to see them. To be sure, there is no sarcasm or irony in that statement. I'd really like to know.

DECLARE @StartDate DATETIME

,@EndDate DATETIME

;

SELECT @StartDate = '31 Dec 2014 23:59:59.997'

,@EndDate = '01 Jan 2016 00:06:59.000'

;

--===== Subtraction method for display

SELECT CONVERT(VARCHAR(10),DATEDIFF(hh,0,@EndDate-@StartDate))

+ RIGHT(CONVERT(CHAR(12),@EndDate-@StartDate,114),10)

;

--===== Subtraction method for decimal hours

SELECT CONVERT(DECIMAL(11,1),(CONVERT(FLOAT,@EndDate-@StartDate)*24.0))

;

{EDIT} Correct spelling on the word "function".