DST Change - OEM start agent failed, agentTZRegion settings

Because of DST change, I saw the agents which were shutdown are not starting, tried manually but no luck.

$ emctl start agent
Oracle Enterprise Manager 10g Release 10.2.0.2.0.
Copyright (c) 1996, 2006 Oracle Corporation. All rights reserved.
Starting agent ...... failed.
The agentTZRegion value in /home/oracle/product/10.2.0/em10g/agent10g/sysman/config/emd.properties is not in agreement with what agent thinks it should be.Please verify your environment to make sure that TZ setting has not changed since the last start of the agent.
If you modified the timezone setting in the environment, please stop the agent and exectute 'emctl resetTZ agent' and also execute the script mgmt_target.set_agent_tzrgn(, ) to get the value propagated to repository.
Consult the log files in: /home/oracle/product/10.2.0/em10g/agent10g/sysman/log

Resolution
In emd.properties you need to correctly set the agentTZRegion value
agentTZRegion=-04:00

And login to OEM repository and run the following SQL to get the present values, so you can reset the value in repdb - login as SYS

select TARGET_NAME, timezone_region FROM mgmt_targets WHERE target_type = 'oracle_emd' AND target_name like '%hostname%';

TARGET_NAME TIMEZONE_REGION
-------------------------- --------------------------
hostname.domainname:2872 -05:00


Now reset the value to correct TZ settings

SQL> exec mgmt_target.set_agent_tzrgn('hostname.domainname:2872','-04:00');
SQL> commit;

Restart the agent, its successful

$emctl start agent
Oracle Enterprise Manager 10g Release 10.2.0.2.0.
Copyright (c) 1996, 2006 Oracle Corporation. All rights reserved.
Starting agent .............................. started.


Good Luck, Cheers