DECLARE @AnyDate DATETIME
SET @AnyDate = GETDATE()

SELECT @AnyDate AS 'Input Date',
  DATEADD(q, DATEDIFF(q, 0, @AnyDate), 0) 
                        AS 'Quarter Start Date',       
  DATEADD(d, -1, DATEADD(q, DATEDIFF(q, 0, @AnyDate) + 1, 0)) 
                        AS 'Quarter End Date'