Considering this table definition
CREATE TABLE [dbo].[Dates](
[StartDate] [datetime] NOT NULL,
[EndDate] [datetime] NOT NULL
)
I assume that if you pass a date you want to know which rows satisfy the condition: startDate < date < EndDate. If this is the case you can use the query:
select *
from Dates
where convert(datetime, '20/12/2010', 103) between StartDate and EndDate;
A stored procedure could look like:
ALTER PROCEDURE [dbo].[GetDataWithinRange]
@p_Date datetime
AS
BEGIN
SELECT *
from Dates
where @p_Date between StartDate and EndDate;
END