It’s a great day for the Irish — and everyone else who chooses to celebrate St. Patrick’s Day.

But March 17 is far more than parades, shamrocks and green beer. Its basis stretches far back in time, to a man now known as Padraig or Patrick. His history, associated legends and other Irish customs have blended together to give us St. Patrick’s Day as we know it.

St. Patrick’s birth and death date is traditionally thought to be March 17. The year of his birth is generally agreed to have been A.D. 390, and he died circa 461. Bear in mind, however, that early sources are prone to error, and the A.D. dating system was not developed until A.D. 525, thus making Patrick’s actual dates a source of scholastic debate.

What is not a matter of debate may come as a surprise: Patrick was not Irish. He was born in Britain, a member of the lower-level Romano-British nobility. According to his autobiographical "Confession," his birthplace was a small villa near "Bannavem Taburniae."

Unsurprisingly, the location of this villa has long since been lost to history. Some allege he was born near Dumbarton, in what is now known as Scotland, while others argue for a location in Wales, and still others advocate the present-day Cotswalds.

At the age of 16, Patrick was abducted by Irish raiders and sold as a slave to a chieftain named Milchu. Raids by Irish pirates were common at this time, as was slavery.

Six years later, Patrick escaped his pagan master (who was alleged to have been a druid priest). A dream told him a ship was waiting to bear him to freedom. Patrick, ever faithful, walked 200 miles to that ship, but his hardships apparently had not ended. He tells of a second stint as a slave, which lasted a few months, and of coming home to a much-changed land, where he was haunted by visions of the Irish begging for his help. When he decided to obey these voices, he ran into resistance and accusations from his elders.

None of this stopped Patrick, who returned and converted many of the Irish to Christianity. (It’s important to remember that some of the Irish already were Christian.) Patrick is also said to have visited other Christian sites, including Glastonbury, in circa A.D. 443. Today, a chapel bearing his name stands on the abbey grounds there .

What may not be true are legends holding Patrick as an advocate of the "Celtic" Church.

Today’s scholars have concluded there is little solid evidence to prove a Christian tradition that was uniquely "Celtic" in content or form. Many traditions cited as Celtic were in fact practiced in Christian churches and communities throughout the world.

Today’s term of choice for the Celtic Church is "the Church in Celtic-speaking lands."

Certain other stories associated with Patrick, while lively and fun, also appear to be myths. These include tales of Patrick driving the snakes out of Ireland (there weren’t snakes there to begin with) and the use of the shamrock to explain the Trinity.

Other tidbits of lore concerning St. Patrick’s Day:

• The shamrock (in Gaelic, seamrog) is the national flower of Ireland, once worn by Irish soldiers in the British Army.

It became a symbol of rebellion in the 19th century, and wearing it was outlawed. Those caught participating in this forbidden "wearing o’ the green" could be punished with hanging.

Today, the shamrock is remembered in the custom of "drowning the shamrock." This little three-leafed clover is dropped into whiskey, picked out and thrown over the left shoulder. It is also picked on St. Patrick’s Day, and worn on the shoulder.

• Green itself was associated with spring in ancient times. It was thought that wearing green clothes would attract the gods responsible for crop growth. While Americans wear green with gusto on March 17, the original color associated with St. Patrick (the man) was "St. Patrick’s blue." According to researcher Christine O’Keefe, the color is not worn in Ireland on St. Patrick’s Day (except as hair ribbons by little girls), because it is a painful reminder of a time when Irish culture was repressed.

• Leprechauns are another example of other traditions being incorporated into St. Patrick’s Day. Leprechauns were spirits associated with Lugh, the ancient Irish god of light. The term derives from lugh chromain, or "little, stopping Lugh," and leprechauns are remnants of Ireland’s pagan past.

• The shillelagh is a walking stick, or a club, named for an oak forest in Co. Wicklow. Shillelaghs were also used in games like hurling, and, less innocently, in warfare and riots. They are now carried as decorative objects in St. Patrick’s Day parades.

• Americans celebrate St. Patrick’s Day with Mass and parades. The first St. Patrick’s Day parade was held in Boston, in 1737. Those less religious or less traditionally minded celebrate the day with dyed beer and bacchanalian revelry.

• St. Patrick’s Day is a legal holiday in Ireland, marked by Mass, parades, plays and concerts in his honor. This year, festivities in Dublin have been canceled, owing to the outbreak of hoof-and-mouth disease.

St. Patrick’s Day, however it is marked, celebrates the Christian historical figure who became Ireland’s patron saint — a remarkable man for a remarkable land.