If you put a format containing both date and time in a datebox, the popup shows a calendar and a timepicker. But the popup is closed after clicking on a date in the calendar, just like in date-only dateboxes. There should be a property for datebox to keep the popup open after a date is selected to allow the user to change the time as well. Right now, they have to open the popup again or force themselves to change the time first, and then select a date.