Hello everyone,Basically, for the DST updates, an outlook update much be applied either on the server or client workstations.Below are the options on the Microsoft Site:The IT administrator has one of four alternatives (pros and cons of each alternative are described below): Run the Exchange Time Zone Update tool against all affected users, servers, or both. Push out the Outlook Time Zone Update tool to the clients and let the users update their own mailboxes. Run the Exchange Time Zone Update tool against all affected users, servers, or both, but only modify recurring appointments. Then ask users to rebook single instance appointments that fall into the extended DST period or ask them to run the Outlook Time Zone Update tool.Run neither the Exchange Time Zone Update tool nor the Outlook Time Zone Update tool. Ask users to examine their calendars and rebook as necessary. IT administrators are strongly advised to refer to the Exchange Time Zone Update tool (930879) and consider all potential effects on their IT environments and user base of those alternatives before running the Exchange Time Link: http://support.microsoft.com/gp/dst_topissues#a2Does anyone know how long it would take to go with option one (Exchange Time Zone Update Tool) with an environment of about 250 users/mailboxes?Thanks

In my experience, each tool you run on each deployment or server takes a different amount of time - there are many factors involved, size of information stores, number of mailboxes, number of "objects" per mailbox which will be effected, general server, O/S, exchange and I/S health etc. The only way to make a safe estimate is to read through the documentation provided for the tool, you will normally be given a rough idea of the max processing speed or average running speed (in this case a pretty detailed table) at the kbI normally like to take the best educated guess at run time according to this information - add on a contingency of 20 - 30% depending on the scenario then use that as my estimated run time.

Depends on the size of the Mailboxes, what kind of Workstation your using, etc. Within Microsoft's MSIT environment we were able to do between 6-7 mailboxes per minute using the rebasing tool