T-SQL (SS2K8) :: Retrieve Dates For Last 7 Days

The following query was used for retrieving dates for the last 7 days . Untill February this query was running fine and would return the last seven days date including today.

SELECT DISTINCT TOP 7 Convert(DateTime, DATEDIFF(DAY, 0, DateCreated)) AS DateCreated,
datepart(dw,DateCreated) AS WeekNum from [TechnologyRepository].[helpdsk].[WorkDetails]
WHERE DATEDIFF(DAY, Convert(DateTime, DATEDIFF(DAY, 0, DateCreated)),GETDATE()) <= 7

However from March (not sure of the exact date)..the query below would only give us 7 days until yesterday..i.e it would list dates from 3/19,3/20,3/21,3/22,3/23,3/24,3/25 and not 3/26 ..

I changed the query to <= 6 and it works as expected. But still not sure why it would not return todays date with <= 7.

SELECT DISTINCT TOP 7 Convert(DateTime, DATEDIFF(DAY, 0, DateCreated)) AS DateCreated,
datepart(dw,DateCreated) AS WeekNum from [TechnologyRepository].[helpdsk].[WorkDetails]
WHERE DATEDIFF(DAY, Convert(DateTime, DATEDIFF(DAY, 0, DateCreated)),GETDATE()) <= 6