Use TEST
GO
CREATE TABLE YourTable 
(PersonID INT 
	, TreatmentID INT
	, StartDate DATETIME
	, EndDate DATETIME
	, TreatmentType INT);
GO
 --PersonID, TreatmentID, StartDate, EndDate, TreatmentType
DElETE FROM YourTable;
INSERT INTO YourTable VAlues (1,1,'01/01/2008','01/02/2008',3) 
go
INSERT INTO YourTable Values( 1,2,'22/01/2008','28/02/2008',1)
go
INSERT INTO YourTable Values( 1,3,'01/04/2008','31/12/2008',2)
go
INSERT INTO YourTable Values( 2,4,'01/01/2008','31/12/2008',1)
go
INSERT INTO YourTable Values( 2,5,'23/06/2008','31/12/2008',3)
go
INSERT INTO YourTable Values( 3,6,'01/01/2008','28/02/2008',1)
go
INSERT INTO YourTable Values( 3,7,'05/11/2008','23/12/2008',2)
go

quote:

---

Msg 242, Level 16, State 3, Line 1
The conversion of a char data type to a datetime data type resulted in an out-of-range datetime value.
The statement has been terminated.

---

INSERT INTO YourTable Values( 1,2,'20080122','20080228',1)