It would be useful to be able to lockout date ranges to a custom start date so that only data available in the startpoint of the database range is available. If a user selects a date range that is previous to data available in the database this could give a false sense of what is being displayed in a viewer.
Along the same lines it would be nice to not allow dates/ times to be selected that are in the future of what the current date is. This would prevent the user from generating a report with a future date in it.