Java and JavaScript in the Database

I create A procedure to Insert Data in database from Oracle Apex Front end , but when I try to save the data it shows an error

my procedure is:

================

create or replace PROCEDURE PURCHASE_PROC (

P_PUR_DATE IN VARCHAR2,

P_SUPPLIER IN NUMBER

)

IS

V_PUR_ID NUMBER:= 0;

BEGIN

BEGIN

SELECT NVL(MAX(PUR_ID),0)+1 INTO V_PUR_ID

FROM PURCHASE;

END;

IF V_PUR_ID > 0 THEN

INSERT INTO PURCHASE (

PUR_ID,

PUR_DATE,

SUPPLIER_ID,

CREATED_BY,

CREATED_DATE

)

VALUES (

V_PUR_ID,

TO_DATE(P_PUR_DATE,'DD/MM/RRRR'),

P_SUPPLIER,

USER,

SYSDATE

);

commit;

END IF;

END;

Error is

======

Technical Info (only available for developers)

• is_internal_error: false
• original_additional_info: ORA-01843: not a valid month
• ora_sqlcode: -1843
• ora_sqlerrm: ORA-01843: not a valid month ORA-06512: at "APEX_220200.WWV_FLOW_PROCESS_NATIVE", line 55 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC_PLSQL", line 126 ORA-06512: at "APEX_220200.WWV_FLOW_DYNAMIC_EXEC", line 2654 ORA-06512: at "WKSP_SOHELJU.PURCHASE_PROC", line 13 ORA-06512: at line 2 ORA-06512: at "SYS.DBMS_SYS_SQL", line 2120 ORA-06512: at "SYS.WWV_DBMS_SQL_APEX_220200", line 837 ORA-06512: at "APEX_220200.WWV_FLOW_DYNAMIC_EXEC", line 2614 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC_PLSQL", line 97 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC_PLSQL", line 430 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC", line 614 ORA-06512: at "APEX_220200.WWV_FLOW_EXEC_LOCAL", line 3053 ORA-06512: at "APEX_220200.WWV_FLOW_EXEC", line 2642 ORA-06512: at "APEX_220200.WWV_FLOW_EXEC", line 2678 ORA-06512: at "APEX_220200.WWV_FLOW_PROCESS_NATIVE", line 34 ORA-06512: at "APEX_220200.WWV_FLOW_PROCESS_NATIVE", line 1230 ORA-06512: at "APEX_220200.WWV_FLOW_PLUGIN", line 3163
• component.type: APEX_APPLICATION_PAGE_PROCESS
• component.id: 52197953560837433711
• component.name: Save
• error_backtrace:
  ORA-06512: at "WKSP_SOHELJU.PURCHASE_PROC", line 13 ORA-06512: at line 2 ORA-06512: at "SYS.DBMS_SYS_SQL", line 2120 ORA-06512: at "SYS.WWV_DBMS_SQL_APEX_220200", line 837 ORA-06512: at "APEX_220200.WWV_FLOW_DYNAMIC_EXEC", line 2614 ORA-06512: at "APEX_220200.WWV_FLOW_PROCESS_NATIVE", line 55 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC_PLSQL", line 126 ORA-06512: at "APEX_220200.WWV_FLOW_DYNAMIC_EXEC", line 2654 ORA-06512: at "WKSP_SOHELJU.PURCHASE_PROC", line 13 ORA-06512: at line 2 ORA-06512: at "SYS.DBMS_SYS_SQL", line 2120 ORA-06512: at "SYS.WWV_DBMS_SQL_APEX_220200", line 837 ORA-06512: at "APEX_220200.WWV_FLOW_DYNAMIC_EXEC", line 2614 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC_PLSQL", line 97 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC_PLSQL", line 430 ORA-06512: at "APEX_220200.WWV_FLOW_CODE_EXEC", line 614 ORA-06512: at "APEX_220200.WWV_FLOW_EXEC_LOCAL", line 3053 ORA-06512: at "APEX_220200.WWV_FLOW_EXEC", line 2642 ORA-06512: at "APEX_220200.WWV_FLOW_EXEC", line 2678 ORA-06512: at "APEX_220200.WWV_FLOW_PROCESS_NATIVE", line 34 ORA-06512: at "APEX_220200.WWV_FLOW_PROCESS_NATIVE", line 1230 ORA-06512: at "APEX_220200.WWV_FLOW_PLUGIN", line 3163 ORA-06512: at "APEX_220200.WWV_FLOW_PROCESS", line 170
• error_statement:
  begin begin PURCHASE_PROC ( P_PUR_DATE => (to_date(:P2_P_DATE, 'MM/DD/YYYY')), P_SUPPLIER => :P2_SUP_ID ); end; end;