Splitting a datetime and replace the year part - sql

Question

I need to split a date like '01/12/15' and replace the year part from 15 to 2015 (ie; 01-12-2015). I get the year by the sql query:
select YEAR('10/12/15')
It returns the year 2015. but I have to replace 15 to 2015. how do i achieve this.
Anyone here please help me. thanks in advance..
Edited:
I've tried following query too..
declare #date varchar='10/12/2015'
declare #datenew date
SELECT #datenew=CONVERT(nvarchar(10), CAST(#date AS DATETIME), 103)
print #datenew
but it throws some error like this :
Conversion failed when converting date and/or time from character string.
How do I change the varchar to date and replace its year part to 4 digit.. please help me..
DECLARE #intFlag INT,#date varchar(150),#payperiod numeric(18,0),#emp_Id varchar(50)
SET #intFlag = 1
declare #count as int set #count=(select count(*) from #myTable)
WHILE (#intFlag <=#count)
BEGIN
select #emp_Id=Employee_Id from #myTable where rownum=#intFlag
select #date=attendance_date from #myTable where rownum=#intFlag
declare #datenew datetime
SELECT #datenew=convert(datetime,CONVERT(nvarchar(10), CAST(#date AS DATETIME), 103) ,103)
It throws the error "The conversion of a varchar data type to a datetime data type resulted in an out-of-range value."

Answer 1

As you said your column is in varchar type, try the following
Query
CREATE TABLE #temp
(
dt VARCHAR(50)
);
INSERT INTO #temp VALUES
('01/12/15'),
('02/12/15'),
('03/12/15'),
('04/12/15'),
('05/12/15');
UPDATE #temp
SET dt = REPLACE(LEFT(dt, LEN(dt) - 2)
+ CAST(YEAR(CAST(dt AS DATE)) AS VARCHAR(4)), '/', '-');
SELECT * FROM #temp;
EDIT
While declaring the variable #date you have not specified the length.
Check the below sql query.
declare #date varchar(10)='10/12/2015'
declare #datenew date
SELECT #datenew=CONVERT(nvarchar(10), CAST(#date AS DATETIME), 103)
print #datenew

Answer 2

The simplest way by casting Date object to VARCHAR
SELECT RIGHT(CAST(YEAR('10/12/15') AS VARCHAR), 2)

Answer 3

If you want to change the format and get the varchar try to use:
SELECT CONVERT(varchar(10), CAST('10/12/15' AS DATETIME), 105)
I hope it helps.

Answer 4

What datatype is the value '01/12/15'?
Maybe this will help you:
SELECT YEAR(CAST('10/12/15' AS DATE))

Answer 5

Problem with your query is that you haven't specified length for varchar datatype:
declare #date varchar(12)='10/12/2015'
declare #datenew date
SELECT #datenew=CONVERT(nvarchar(10), CAST(#date AS DATETIME), 103)
print #datenew

Answer 6

Try using:
Declare #date nvarchar(20)='10/12/15'
Declare #datenew nvarchar(40)
SELECT #datenew=CONVERT(nvarchar(10), CAST(#date AS DATETIME), 103)
Print #datenew