this says "An individual who does not profess to hold any religious belief, or does not wish to swear by their religious beliefs may make an affirmation, reciting the words 'I do solemnly, sincerely and truly declare and affirm that...'
The 'affirmation' is not technically an oath, as there is no appeal to a sacred witness, however, the practical purpose is the same and it holds the same status under law."
not sure if this applies to everything, i.e not just in court.