It depends on the region. You can find more information here: http://business.brookes.ac.uk/alumni/graduations/regional/
Currently the Graduations for the OBU Degree are held in UK, UAE, Singapore and Malaysia. The graduation for P31 in Singapore and Malaysia are scheduled to be held in the 3rd / 4th week of Oct 2016 and you may get in touch with OBU directly to find out the dates for the other locations.
In fact OBU would have got in touch with all graduates directly to inform them on the possible options for the Graduations and the dates.