サマータイム(DST)のアップデータ：Microsoft

WM5 PC

To display correct date in your Windows Mobile devices, download this update!
Updating Windows Mobile-powered devices for the new Daylight Saving Time
Congress has changed the dates for Daylight Saving Time (DST) in the United States starting in 2007. Canada has adopted similar DST dates. These changes could cause clocks and Microsoft Outlook calendar appointments on Windows Mobile-powered devices to display incorrect times for March 11 ・April 1, 2007 and October 28 ・November 4, 2007 and again in subsequent years. You can find more information about the exact dates and potential impact in the Changes in DST section.

msmobiles.comで知りましたがアメリカ、カナダ、メキシコの日本で言うサマータイム、現地ではDaylight Saving Time(DST)が今年から変更となりそれにあわせたアップデータが公開されたようです！
とりあえず北米に行く方やお住まいの方はアップデートしておいたほうがいいかもですね？