Just saw your answer, thanks.
I use JsDate to get the UTC conversion. However this still doesn't work for the picker, as it will still display the date using the local time format. If I have 12/04/2012 at 1am UTC in the US, it will show me the picker at 11/04/2012. May be the solution would be to pass a "converted" date to the picker, ie add the time offset to the data when opening the picker. I do not use the DateBox but my own widget, so I can pass the date I want to the picker.