Detect if two time periods overlap
I realize this has been answered before on Stack Overflow. It got me going in the right direction.  

I now realize I should add the actual time stamp of the leave to my Start and End Dates and do a simple compare. I wish I had figured this out months ago; it would have saved me much pain and suffering.

For anyone in the future who has a similar issue:


My new StartDate will be recorded as 08/22/2015 09:00.000 instead of 08/22/2015 00:00.000
The EndDate will be 8/23/2015 13:00:00.000


I can then compare as per the linked answer:

(
    (@Start &gt; StartDate and @Start &lt; EndDate)
    OR (@End &gt; StartDate and @End &lt; EndDate)
    OR (@Start &lt; StartDate and @End &gt;EndDate)
)