Error code 1292 Mysql DateTime - mysql

Question

I am trying to format a date and a time that comes in one column called DATE as DD/MM/YYYY (Varchar) and in another column called TIME as HH:MM:SS into one variable to insert into another column (in Datetime data type). The code below is my procedure.
DROP PROCEDURE IF EXISTS TESTProc;
DELIMITER //
CREATE PROCEDURE TESTproc()
BEGIN
DECLARE LYEAR VARCHAR(45);
DECLARE LMONTH VARCHAR(45);
DECLARE LDAY VARCHAR(45);
DECLARE LTIME VARCHAR(45);
DECLARE LDATETIME DATETIME;
SELECT TIME FROM db.test_table INTO LTIME;
SELECT SUBSTRING(DATE,6,4) FROM db.test_table INTO LYEAR;
SELECT SUBSTRING(DATE,3,2) FROM db.test_table INTO LMONTH;
SELECT SUBSTRING(DATE,1,1) FROM db.test_table INTO LDAY;
SELECT CONCAT(LYEAR,'-', LMONTH,'-','0',LDAY,' ',LTIME) INTO LDATETIME;
INSERT INTO db.test_table(VC19) VALUES (LDATETIME);
END //
Call TESTProc;
When I run the procedure, I get an error code back:
Call TESTProc; Error Code: 1292. Incorrect datetime value: '2013-31-01 16:00:40' for column 'LDATETIME' at row 2
I only have one row in db.test_table. I do not have a column in the table called 'LDATETIME', this is just my local variable. I can see from the error that my format is correct for the DateTime 'YYYY-MM-DD HH:MM:SS'.
why I am getting this error?
Update: Here is how my code looks now:
DROP PROCEDURE IF EXISTS DateProc;
DELIMITER //
CREATE PROCEDURE Dateproc()
BEGIN
DECLARE LTIME VARCHAR(45);
DECLARE LDATE VARCHAR(45);
DECLARE LDATETIME DATETIME;
SELECT TIME FROM db.date_table INTO LTIME;
SELECT DATE FROM db.date_table INTO LDATE;
IF LENGTH(LDATE) = 9 AND SUBSTRING(LDATE,2,1) = '/'
THEN SET LDATETIME = CONCAT(SUBSTRING(LDATE,6,4),'-0',SUBSTRING(LDATE,1,1),'-',SUBSTRING(LDATE,3,2), ' ', LTIME);
ELSE IF LENGTH(LDATE) = 9 AND SUBSTRING(LDATE,3,1) = '/'
THEN SET LDATETIME = CONCAT(SUBSTRING(LDATE,6,4),'-',SUBSTRING(LDATE,1,2),'-0',SUBSTRING(LDATE,4,1), ' ', LTIME);
ELSE IF LENGTH(LDATE) = 10
THEN SET LDATETIME = CONCAT(SUBSTRING(LDATE,7,4),'-',SUBSTRING(LDATE,1,2),'-',SUBSTRING(LDATE,4,2), ' ', LTIME);
ELSE IF LENGTH(LDATE) = 8
THEN SET LDATETIME = CONCAT(SUBSTRING(LDATE,5,4),'-0',SUBSTRING(LDATE,1,1),'-0',SUBSTRING(LDATE,3,1), ' ', LTIME);
END IF;
END IF;
END IF;
END IF;
INSERT INTO db.date_table(table_name) VALUES (LDATETIME);
END //
CALL DateProc;
This seems to work and accounts for any variable date that may end up in my original date column.

Answer 1

Look at the value:
'2013-31-01 16:00:40'
That's trying to use a month of 31.
It's not clear whether that just means your test data is wrong, or whether you need to change these lines:
SELECT SUBSTRING(DATE,3,2) FROM db.test_table INTO LMONTH;
SELECT SUBSTRING(DATE,1,1) FROM db.test_table INTO LDAY;
to:
SELECT SUBSTRING(DATE,1,2) FROM db.test_table INTO LMONTH;
SELECT SUBSTRING(DATE,4,2) FROM db.test_table INTO LDAY;
Note the change from 1 to 2 for the substring starting at 1 anyway, and the change of the second starting position from 3 to 4. You want two-digit month and day values, right? If your data format is actually D/M/YYYY (i.e. only using two digits when they're required) then you won't be able to use fixed substring positions.

Answer 2

Somehow your LMONTH and LDAY values seem to be reversed as LMONTH is getting written as 31 and LDAY as 01 - which obviously incorrect. Check the data within your source table.