Consider this SQL SELECT statement:

    [dbo].[TimeSheet] [TS]
    ([TS].[EntryDate] = @ActivityStartDate)

Seems pretty straight forward, but you run into some issues when comparing dates with timestamps. If @ActivityStartDate is passed into the query as 6/1/2014 12:00 AM, because a specific time was never specified, but the timesheet entries contain timestamps, then you run into some inconsistencies. For example, if the Timesheet date is equal to 6/1/2014 10:00 AM, then the row will not be returned because the Timesheet date evaluates to LESS THAN the parameter. You can use the DATEDIFF method to resolve this:

DATEDIFF(DAY, [TS].[EntryDate], @ActivityStartDate) = 0

Or you can simply remove the timestamp:

DATEADD(DD, DATEDIFF(DD, 0, [TS].[EntryDate]), 0) = @ActivityStartDate