Oracle Server Time

when we access oracle server from CLIENT then date and time come from Oracle Server Machine not from Oracle client machine.

E:\>sqlplus "scott/tiger@hgc"
SQL*Plus: Release 10.1.0.2.0 - Production on Thu Feb 1 17:12:23 2007
Copyright (c) 1982, 2004, Oracle.
All rights reserved.
Connected to:Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options

SQL> alter session set nls_date_format = 'dd-mon-yyyy hh24:mi:ss';
Session altered.

SQL> select sysdate from dual;
SYSDATE
--------------------
01-feb-2007 16:13:00---->Server Machine time ( Oracle Server)

SQL> host time
The current time is: 17:12:35.56--> my local machine time ( Oracle Client)
Enter the new time:

NO need to restart Oracle Server when you change OS time ( LOCAL MACHINE).

E:\>sqlplus "sys as sysdba"
SQL*Plus: Release 10.1.0.2.0 - Production on Thu Feb 1 17:14:18 2007
Copyright (c) 1982, 2004, Oracle.
All rights reserved.
Enter password:
Connected to:Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options

SQL> alter session set nls_date_format = 'dd-mon-yyyy hh24:mi:ss';
Session altered.

SQL> select sysdate from dual;
SYSDATE
--------------------
01-feb-2007 17:14:24

SQL> host time
The current time is: 17:14:26.62
Enter the new time:

SQL>--change my OS machine time from 17:14 to 16:14.

SQL> select sysdate from dual;
SYSDATE
--------------------
01-feb-2007 16:14:42

SQL> host time
The current time is: 16:14:44.80
Enter the new time: