Yes, it is possible to start on the 20th or 21st of August. If so, please remark this when you sign up for the AID at www.aidwageningen.nl.
If you are not able to start the AID on the 18th of August or if you start later than 12:00 hours you can register in the Forum building (Droevendaalsesteeg 2) in room C103. There is the temporary AID office. If you register you will get your AID bag, AID t-shirt (if you ordered it) and your wristband. Your AID wristband will grant you entrance to the different AID program parts. Without a wristband you will not have access to the AID program. Therefore it is really important that you register as soon as possible! The AID office is opened from early in the morning till late in the evening. It is located in the Forum Building, room 103.