Owao... M$ seems to be pretty interested providing patch for BD windows users !! :D Check the following notice :
Notice: Optional Fix-it Available for Bangladesh 2009 Daylight Saving Time
As reported in the Bangladesh Government’s Gazette, Bangladesh has announced the introduction of Daylight Saving Time (DST). The start of DST for 2009 is on June 19th at 11:00 PM.
Microsoft has produced an automated workaround (called a fix-it) to implement the DST Start time change for Windows XP, Windows Server 2003, Windows Vista and Windows Server 2008. The Fix it solution is a MSI file so it is deployed as any other MSI based software package.
If interested in downloading this workaround please refer to KB972423 titled:”An optional update is available to update the Daylight Saving Time for Bangladesh for the year 2009 for Windows XP, Windows Server 2003, Windows Vista and Windows Server 2008 based computers”
For other Windows versions, please refer to KB 914387 “How to configure daylight saving time for Microsoft Windows operating systems” on how to update the time zone registry key.