Core Issue
Firewall or Antivirus software can prevent the proper application of the daylight saving time (DST) patch. In these cases, the DST patch does not run.
Resolution
In order to fix the problem, disable any Firewall or Antivirus software that runs on the system. Also, disable the Cisco Security Agent (CSA) from services. Refer the document Update the Cisco CallManager, the IP Phones, the MCSs and the Cisco Unity to support the changes to DST in March 2007.
