Let's start with what most people think they know. We have been told that Patrick was a Catholic monk who brought the Trinity doctrine to the people of Ireland. And along the way he drove all the snakes from the Emerald Isle. He became so renowned that the Catholic Church made him a "saint." None of that is true!
Patrick was Scottish!
Patrick's given name was actually Maewyn Succat (or Sucat). He took the name Patrick most likely because of the area he was from in Scotland. That's right, Patrick was Scottish, not Irish! Here's what Patrick said himself of his background: " I, Patrick…had Calpornius for my father, a deacon, a son of the late Potitus, the presbyter, who dwelt in the village of Banavan…I was captured. I was almost sixteen years of age…and taken to Ireland in captivity with many thousand men" (William Cathcart, D. D., The Ancient British and Irish Churches , p.127).
Patrick labored for six years as a slave until he managed to escape back to his native Scotland around A.D. 376. He believed he had a calling from God, however, to go back to Ireland to teach God's Word to the people there. The Catholic Church, while having had an impact in England and later Scotland, did not have a significant foothold in Ireland until the 12th century. They didn't even acknowledge Patrick for about 200 years after his death. Patrick was connected to what is known as the Celtic Church. It was very much opposed to what was taught in the Roman Catholic Church.
Patrick did not follow Roman Catholic doctrine
While we have little of Patrick's history and teaching written by himself, what's taught about Patrick now didn't surface until about 500 years after his death. It was the Catholic priest Jocelyn, writing around A.D. 1130 who wrote most extensively about Patrick. He ignored much of what was known then about Patrick and inserted a Catholic background into Patrick's story. Patrick never wrote about a connection to Rome or popes or that his authority came from there. So if Patrick wasn't Roman Catholic, what did he teach?
In A.D. 596 Pope Gregory sent a group of monks to England to try and bring the Celtic Church under the authority of Rome. However, the Celts refused to acknowledge Gregory's authority and rejected the teachings of the Roman Church. In Ireland the monks found that the Celtic Church permitted their priests to marry. They also practiced baptism by full immersion in water. The Celtic Church also rejected the doctrine of (papal) infallibility and veneration, transubstantiation, the confessional, the Mass, relic worship, image adoration and the primacy of Peter (Truth Triumphant , by B.G. Wilkinson, pg. 108). The latter list is of specific Roman Catholic doctrines that the Celtic Church knew were not taught in the Scriptures.
Patrick observed the Saturday Sabbath, Passover and rejected the Trinity doctrine
Patrick also rejected the merging of church and state (a main teaching of Catholicism). He believed and taught the same as Jesus in John:18:36 that God's Kingdom is not of this world. The Celtic Church had local ecclesiastical councils and kept Saturday as a day of rest, (A.C. Flick, The Rise of Medieval Church, pp. 236-327). In this matter of a Saturday (Sabbath) rest, Dr. James C. Moffatt wrote that, "They [the Celtic churches] obeyed the fourth commandment [the Sabbath commandment] literally upon the seventh day of the week" (The Church in Scotland , pg. 140).
Patrick (and the Celtic Church) observed the other "festivals of the Eternal" (Leviticus 23), believed human beings were mortal (that is rejected the teaching of an immortal soul and the doctrine of going to heaven or hell), rejected the Trinity doctrine, followed the food laws of Leviticus 11, refused veneration of "saints" or worship of Mary, and believed that only Jesus Christ is our mediator (Leslie Hardinge, The Celtic Church in Britain ; B.G. Wilkinson, Truth Triumphant ).
The Celtic Church had a long history before the Catholic Church pushed deeper into England, Scotland and Ireland. Celtic writings speak of individuals coming from Asia Minor who brought with them the doctrines they received from John, Paul, Philip and other apostles of Jesus. A Catholic "father," Bede, (who lived in the mid 700s A.D.) who wrote about the Celtic Church: "They ignorantly refuse to observe our Easter [Pascha, or Passover] on which Christ was sacrificed, arguing that it should be observed with the Hebrew Passover on the fourteenth of the moon" (Bede, Historia Ecclesiastica ).
Is Saint Patrick's Day in the Bible?
Saint Patrick's Day is not a biblical holiday or Holy Day. And, as it is currently celebrated, St. Patrick's Day actually has nothing to do with the historical man Patrick. Many "Christian" holidays are a mixture of truth and error. Because of this, most people don't really know the history or purpose of the day. We encourage you to read what God said in the Bible to know which Holy Days He made and who He said are saints. The United Church of God traces its origins to the Church that Jesus founded in the early first century. We follow the same teachings, doctrines and practices established then, and believe our commission is to proclaim the gospel of the coming Kingdom of God to all the world as a witness and teach all nations to observe what Christ commanded.
It appears that Patrick believed these same teachings. We encourage you to read the online Bible study aids, Fundamental Beliefs of the United Church of God and The Church Jesus Built to learn more about what individuals like Patrick taught and what we teach from Scripture. From our best historical understanding, the Patrick you didn't know lived a life according to the Bible, rather than human traditions. You can too.