For multi-day events visitors will have to present a valid Covid certificate every time they access the event location. Spending the night at the campsite is allowed on condition that your certificate is still valid.
If your certificate should expire during your presence (e.g. a test certificate that expires at 10 a.m.) you are allowed to stay until midnight.
Based on a valid Covid certificate, the organisers of a multi-day test or pilot project or mass event can provide visitors with a means (e.g. a wristband) to indicate the validity period of the Covid certificate, on the basis of which the user can access the event without getting tested (again) or having the Covid Safe Ticket scanned again.