How to derive exact days, hours and minutes between two dates.

The difference between February 8th at 7:52 AM and February 14th at 3:34 PM is indeed 6 days, 7 hours, and 42 minutes.

2/8 @ 07:52 - 2/9 @ 07:52 = 1 day
2/9 @ 07:52 - 2/10 @ 07:52 = 1 day
2/10 @ 07:52 - 2/11 @ 07:52 = 1 day
2/11 @ 07:52 - 2/12 @ 07:52 = 1 day
2/12 @ 07:52 - 2/13 @ 07:52 = 1 day
2/13 @ 07:52 - 2/14 @ 07:52 = 1 day
2/14 @ 07:52 - 2/14 @ 15:34 = 7 hours, 42 minutes

Check out Jeff Moden's outstanding post on time differences for a way to calculate the difference in various formats. He did a great job explaining the concept, I think. Later on in the thread, GSquared has another method for getting the values, and it looks like this:

declare @BeginDate datetime = '2011-02-08 07:52';
declare @EndDate datetime = '2011-02-14 15:34';

select 
datepart(year, @EndDate - @BeginDate)-1900 as years,
datepart(month, @EndDate - @BeginDate) - 1 as months,
datepart(day, @EndDate - @BeginDate) - 1 as days,
datepart(hour, @EndDate - @BeginDate) as hours,
datepart(minute, @EndDate - @BeginDate) as minutes,
datepart(second, @EndDate - @BeginDate) as seconds;

This query has some problems with edge cases, so beware if your query needs to span more than one year.