RIM released two PDF documents to address this issue of DST March 2007.

You can download them here:Impact of North American Daylight Saving Time changes in 2007 on BlackBerry device users

The standard dates for North American Daylight Saving Time (DST) change in March 2007. Previously, DST began on the first Sunday in April and ended on the last Sunday in October. As of March 2007, DST begins on the second Sunday in March and ends on the first Sunday in November. For more information, see Sec.110 of the Energy Policy Act of 2005.
When the DST dates change in March 2007, BlackBerry® devices will not update their clocks for the affected time zones if no patches for impacted BlackBerry software and third party software (e.g. for Microsoft® Windows see www.microsoft.com/windows/timezone/dst2007.mspx) are applied. As a result, your BlackBerry device might not display correct time zone information for certain time periods during the year. See Planned Resolutions to review specifics in various situations.
Appointments and their reminders might appear 1 hour late on your BlackBerry device if the appointments start in one of the following windows in any year:
  • Between the second Sunday in March and the first Sunday in April (for example, 11 March 2007 to 1 April 2007)
  • Between the last Sunday in October and the first Sunday in November (for example, 28 October 2007 to 4 November 2007)
NOTE: Anyone living in or traveling to Mexico will not be impacted by the DST change as Mexico is not changing the DST start and end dates. However, any Mexico, Latin America, European, or Asia-Pacific users who book meetings with US or Canadian-based users will also be impacted by this transition for those meetings unless patches are applied.Discuss here