The format of the time chunk is represented by the number of minutes from the start of the month to the beginning of the chunk and from the start of the month to the end of the chunk.
These two points in time are called the DTStart and DTEnd properties.
Although Tech Net and the Exchange development team blog (at provide good information about free/busy data, this article aims to give you comprehensive coverage of the topic, bringing different sources of information together to illuminate one of the more esoteric parts of Exchange.
Let’s start demystifying free/busy data by looking at where Exchange stores it and how clients publish it.
However, replication of free/busy data affects how current, and thus how accurate, the data is for users trying to schedule meetings.
If your Exchange implementation stores only one copy of the free/busy information for a user, Outlook must connect to that folder on a specific server in the organization.
Where Free/Busy Data Resides All pre–Exchange Server 2007 versions of Exchange use a public folder to store the data that clients use to calculate when users are available.
Exchange Server 20 servers store free/busy data in the SCHEDULE FREE BUSY\Admin Group public folder.
If that server is close (in network terms), you’ll get acceptable performance and the free/busy data will be up-to-date and accurate.
However, in a distributed organization, you might want to replicate free/busy data to several public folder servers so that users can access local copies of the data.
In addition, Exchange merges consecutive appointments together to form one chunk of busy time.
Thus, when you view another user’s calendar and see that he or she is busy between 10pm, you can’t tell whether the user has one long appointment or several shorter meetings.
Exchange updates the data for OWA clients through the MSExchange FBPublish process, which runs as part of the System Attendant service.