St. Patrick kept Saturday as the sabbath. During the first century the Roman Empire did not extend into Scotland and Ireland. The Roman Empire made several attempts to conquer Scotland to no avail. The Romans eventually build a wall between Scotland and England called Adrian Wall. Remnants of that wall are still present today. Therefore the beliefs of the early Catholic Church did not get infiltrated into Scotland and Ireland until must later in History. Below are 4 Historical references proving that Saturday not Sunday was kept as the day of worship in Ireland and Scotland.
1) Historian A. C. Flick writes:
“The Celts used a Latin Bible unlike the Vulgate, and kept Saturday as a day of rest, with special religious services on Sunday.”
The Rise of the Medieval Church, page 237, Flick.
2) “It seems to have been customary in the Celtic churches of early times, in Ireland as well as Scotland, to keep Saturday, the Jewish Sabbath, as a day of rest from labor. They obeyed the fourth commandment literally upon the seventh day of the week.”
The Church in Scotland, page140, James C. Moffatt, D.D.
3) “In this latter instance they seemed to have followed a custom of which we find traces in the early monastic church of Ireland by which they held Saturday to be the Sabbath on which they rested from all their labours.”
Adamnan Life of St. Columba, page 96), W.T. Skene
4) From the Catholic historian, T. Ratcliffe Barnett, on the Catholic queen of Scotland: “In this matter the Scots had perhaps kept up the traditional usage of the ancient Irish Church WHICH OBSERVED SATURDAY INSTEAD OF SUNDAY AS THE DAY OF REST.”
St Patrick was not Catholic
St Patrick was not a Catholic, in fact during his life time he had several conflicts with the Catholic Church. Patrick lived 100 years at least after the Council Nicaea and he condemned its teaching. The Council of Nicaea setup Sunday as the sabbath day and stopped Saturday worship. It also incorporated many pagan traditions into the Roman church. Before the Council of Nicaea even the Roman Empire kept the seventh day sabbath. When the pope sent a Bishop to Ireland, Patrick refused to bow to him. In fact the Pope Boniface condemned the Scotish and Irish for allowing their priest to marry. In fact allowing the priest to marry was major bone of contention between the Catholic Church and Ireland.
“The monks sent to England (in 596 A.D.) by Pope Gregory the Great soon came to see that the Celtic Church differed from theirs in many respects…Augustine himself (a Benedictine abbot)…held several conferences with the Christian Celts in order to accomplish the difficult task of their subjugation (submission) to Roman authority…The Celts permitted their priests to marry, the Romans forbade it. The Celts used a different mode of baptism (i.e., true baptism: immersion) from that of the Romans…The Celts held their own councils and enacted their own laws, independent of Rome. The Celts used a Latin Bible (i.e., the Itala) unlike the (Roman Catholic’s Latin) Vulgate, and kept Saturday as a day of rest.”
The Rise of the Medieval Church, page 236-237, Flick.
Therefore it is plain to see that the Catholic Church invented false history about St Patrick trying to proof he was a Catholic priest. But history does not back that up. However there was a papal hero –Palladius, who name was also Patrick. He was sent from Rome to Ireland.
 Ecclesiastical History of Ireland, vol. 1, pp. 12-15, Killen.
 St. Patrick, His Life and Teaching, page 33, note 1, Newell.