In a Microsoft Exchange Server 2007 Unified Messaging (UM) environment, you can set the time for the Business Hours from the properties menu of UM Auto Attendant.
The business hours greeting and nonbusiness hours greeting are played based on the "Business Hours" schedule. When daylight saving time (DST) changes, the schedule is not adjusted. Therefore, the time for the call routing and custom greeting mechanism shift by 1 hour. Because of this behavior, the Auto Attendant presents nonbusiness hours greetings and route calls during business hours accordingly. Additionally, the callers cannot reach the desired person or Department.
To resolve this problem, install the following update rollup:
972076 Description of Update Rollup 2 for Exchange Server 2007 Service Pack 2
To work around this problem, adjust the business hours manually.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.