SQL Server 2012 :: Passing Date Parameter To Stored Procedure?

I am trying to pass a date parameter to a stored procedure.

I pass the actual date as a string but keep getting errors that the string variable cannot be converted to a date whatever I do.

Basically, this works:

DECLARE @DDate DATETIME
SET @DDate = convert(datetime, '2004-01-01',101 )

But this returns an error:

DECLARE @strdate VARCHAR
SET @strdate = '2004-01-01'
DECLARE @DDate DATETIME
SET @DDate = convert(datetime, @strdate,101 )

What am I doing wrong?