Despite claims that the first Christian services were held in the new colony around Circular Quay on 3rd February(see photograph above) , it is much more likely that Receveur and Mongez would have held mass not long after landing on the 26th or 27th January 1788 (which was a Sunday). Brochures about Pere Receveur and the first Christian services available for download:
La Perouse Museum & Headland 
It is a moral certainty that the Priest would have celebrated Mass at least on the Sunday, but most likely each day either aboard ship or ashore when practicable.