Getting datetime of the system

Hello,
I am using GETDATE() in my SQL statement but I've got this error  when I run my windows application form:

Additional information: Conversion failed when converting date and/or time from character string.

This is the stored procedure
USE [PharmacyDB]
GO
/****** Object:  StoredProcedure [dbo].[storedP]    Script Date: 2014-06-07 00:54:28 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER proc [dbo].[storedP]
(@prdctName nvarchar(50)
,@ordrdQnty int
--,@OrderID int
,@ordrPrice money
,@TrnDate datetime = GETDATE
--,@TrnTotal decimal=90.000
)

as
BEGIN TRY
begin transaction trs

DECLARE @TrnId int
SET @TrnId = 'SCOPE_IDENTITY'

INSERT INTO [dbo].[OrderProduct]
(--[OrdrId],
[prdctName]
,[ordrdQnty]
,[ordrPrice]
--,[TrnId]
)
VALUES
(--@OrderID,
@prdctName
,@ordrdQnty
,@ordrPrice
--,@TrnId
)

INSERT INTO [dbo].[Transaction]
(
--[OrdrId],
[TrnDate]
--,[TrnTotal]
)
VALUES
(-- @OrderId ,
     -- CONVERT(timestamp,GETDATE())          
      GETDATE()
--(select  CURRENT_TIMESTAMP )
 --,@TrnTotal
-- (SELECT
-- t1.OrdrId,
--       t1.ordrPrice,
--       SUM(t2.ordrPrice) AS SUM
--FROM OrderProduct t1
--INNER JOIN OrderProduct t2 ON t1.OrdrId >= t2.OrdrId
--GROUP BY t1.OrdrId,
--      t1.ordrPrice   
--ORDER BY (t1.OrdrId)
--    )
 )

commit tran
return 0
END TRY
BEGIN CATCH
rollback
return 1
END CATCH

Thanks in advanced.

ALTER proc [dbo].[storedP]
(@prdctName nvarchar(50)
,@ordrdQnty int
--,@OrderID int
,@ordrPrice money
,@TrnDate datetime = NULL-- GETDATE
--,@TrnTotal decimal=90.000
)

as
BEGIN TRY
begin transaction trs

DECLARE @TrnId int
SET @TrnId = 'SCOPE_IDENTITY'

INSERT INTO [dbo].[OrderProduct]
(--[OrdrId],
[prdctName]
,[ordrdQnty]
,[ordrPrice]

)
VALUES
(
@prdctName 
,@ordrdQnty 
,@ordrPrice

)
 
 IF @TrnDate IS NULL 

   SET @TrnDate = CURRENT_TIMESTAMP;

INSERT INTO [dbo].[Transaction]
(

[TrnDate]
--,[TrnTotal]
)
VALUES
(        
	  GETDATE()

 --,@TrnTotal
-- (SELECT 
-- t1.OrdrId,
--       t1.ordrPrice,
--       SUM(t2.ordrPrice) AS SUM
--FROM OrderProduct t1
--INNER JOIN OrderProduct t2 ON t1.OrdrId >= t2.OrdrId 
--GROUP BY t1.OrdrId,
--      t1.ordrPrice   
--ORDER BY (t1.OrdrId)
--	) 
 )

commit tran
return 0
END TRY
BEGIN CATCH 
rollback
return 1
END CATCH