Converting Date Data Type In Stored Procedure

HI Experts...

I am using SQL SERVER 2005 standard edition

I have encountered a problem regarding converting date data type in stored procedure

As i was having problem taking date as input parameter in my stored procedure, so, then  I changed to varchar (16) i.e.

CREATE PROCEDURE sp_CalendarCreate
                                      @StDate VARCHAR(16) ,
                                      @EDate VARCHAR(16),

then I am converting varchar to date with following code

DECLARE @STARTDATE DATETIME
DECLARE @ENDDATE DATETIME

SELECT @STARTDATE = CAST(@STDATE AS DATETIME)
SELECT @ENDDATE = CAST(@EDATE AS DATETIME)

When I try to execute the procedure with following code

execute sp_CalendarCreate @stdate='12-1-06',@edate='20-1-06'

but it gives me following error

Msg 242, Level 16, State 3, Procedure sp_CalendarCreate, Line 45
The conversion of a char data type to a datetime data type resulted in an out-of-range datetime value.

Can any one tell me the  solution of that problem (at ur earliest)

regards,

Anas