To further confuse the issue, St. Patrick is considered a saint by the Eastern Orthodox churches. It makes perfect since, inasmuch as he lived and died before the Great Schism. All saints considered to be so by the Roman church prior to 1054 are also saints in Orthodoxy.
UPDATE: I was mistaken. I am now being informed that this isn’t strictly true, that many, but not all, Western saints from the pre-schism days are venerated by the East. St. Augustine is a notable example; the East views him as a holy man, but not a saint, owing to what Orthodoxy holds to be certain theological errors.