Datepicker: How to set start month in Calendar mode

I use the DatePicker in the Calendar mode and when the bind-value is not set the calendar shows the current date.
How to change this to another month + year without setting the bind-value because the user still needs to pick the date.
I just want to help him by moving the calendar to the allowed date range, which is typically 2-3 months in the future.

Thanks,
Paul