1171 Henry II of England declares himself Lord of Ireland

Henry II of England (1133 - 1189, also known as Henry Curtmantle, Henry FitzEmpress or Henry Plantagenet) invaded Ireland to control Strongbow (Richard de Clare, 2nd Earl of Pembroke, alias 'Strongbow', who he feared was becoming a threat to the stability of his own kingdom on its western fringes) and other Norman lords. In furtherance of the Norman invasion of Ireland, King Henry II of England landed at Waterford. Waterford and then Dublin were declared royal cities, with Dublin also declared capital of Ireland. In the process he accepted the fealty of the Gaelic kings at Dublin in November 1171, and he summoned the Synod of Cashel in 1172, which brought the Irish Church into conformity with English and European norms. 

1014 Decline of Viking power in Ireland

Brian Boru (941 – 1014) was an Irish king who ended the domination of the High Kingship of Ireland by the Uí Néill (Irish and Scottish dynasties). In 1014, Brian's armies confronted the armies of Leinster and Dublin at Clontarf near Dublin on Good Friday. The resulting Battle of Clontarf was a bloody affair, with Brian, his son Murchad, and Máel Mórda among those killed. It pitted the forces of Brian Boru, against a Viking-Irish alliance comprising the forces of Sigtrygg Silkbeard, king of Dublin, Máel Mórda mac Murchada, king of Leinster, and a Viking contingent led by Sigurd of Orkney and Brodir of Mann. 

988 Malachy II High King of Ireland

In 980 Olaf Cuarán, King of Dublin, was defeated by Máel Sechnaill at Tara. Máel Sechnaill followed up his victory with a siege of Dublin which surrendered after three days and nights. Máel Sechnaill mac Domnaill (948 - 1022), also called Máel Sechnaill Mór, Máel Sechnaill II, anglicized Malachy II, was King of Mide and High King of Ireland. His great victory at the Battle of Tara against Olaf Cuaran resulted in Gaelic control of the Kingdom of Dublin and as a result the founding of Dublin is counted by some from the year 988, although a village had existed on the site of Dublin since before the Roman occupation of Great Britain nearly a thousand years earlier.

830 Last vestiges of paganism in Ireland

The Martyrology of Tallaght, which is closely related to the Félire Oengusso or Martyrology of Óengus the Culdee, is a list of saints and their feast days assembled by Máel Ruain and/or Óengus the Culdee at Tallaght Monastery, near Dublin. The Martyrology of Tallaght is in prose and contains two sections for each day of the year, one general and one for Irish saints. It also has a prologue and an epilogue. Based on oral traditions and on older texts, the work may have been first completed in 790. However, Pádraig Ó Riain of University College, Cork, a leading authority, has argued that the Martyrology of Tallaght and the Martyrology of Oengus date from about 830. Ó Riain has shown that the general sections of the Martyrology of Tallaght are based on a Northumbrian copy of the Martyrologium Hieronymianum. In 2000, the manuscript came into the possession of University College, Dublin.

664 Yellow fever on the island

Historically known as yellow jack or yellow plague, is an acute viral disease. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains particularly in the back, and headaches. The evolutionary origins of yellow fever most likely lie in Africa, with transmission of the disease from primates to human beings. The disease is caused by the yellow fever virus and is spread by the bite of the female mosquito. It only infects humans, other primates, and several species of mosquitoes. A safe and effective vaccine against yellow fever exists and some countries require vaccinations for travelers.

536 Crop failure and famine

The extreme weather events of 535–536 were the most severe and protracted short-term episodes of cooling in the Northern Hemisphere. Its effects were widespread, causing unseasonal weather, crop failures, and famines worldwide. The event is thought to have been caused by an extensive atmospheric dust veil, possibly resulting from a large volcanic eruption in the tropics, and/or debris from space impacting the Earth. Further phenomena was reported by a number of independent contemporary sources as low temperatures, even snow during the summer. "A dense, dry fog" in the Middle East, China, and Europe or Drought in Peru, which affected the Moche culture.

432 Saint Patrick returns to Ireland

Saint Patrick was a 5th-century Romano-British Christian missionary and bishop in Ireland. Known as the "Apostle of Ireland", he is the primary patron saint of Ireland along with Saints Brigit and Columba. He is generally credited with being the first bishop of Armagh, Primate of Ireland. When he was about 16, he was captured from his home in Great Britain by Irish Pirates, and taken as a slave to Ireland, where he lived for six years before escaping and returning to his family. After becoming a cleric, he returned to northern and western Ireland. By the seventh century, he had already come to be revered as the patron saint of Ireland. Saint Patrick's Day is observed on 17 March, the date of his death. It is celebrated inside and outside Ireland as a religious and cultural holiday. In the dioceses of Ireland, it is both a solemnity and a holy day of obligation; it is also a celebration of Ireland itself.

300 Pollen data

The Irish Iron Age began around 500 BC and continued until the Christian era in Ireland, which brought some written records and therefore the end of prehistoric Ireland. The late Iron Age saw sizeable changes in human activity. Pollen data extracted from Irish bogs indicates that "the impact of human activity upon the flora around the bogs from which the pollen came was less between c. 200 BC and c. 300 AD than either before or after." The third and fourth centuries saw a rapid recovery. The reasons for the decline and recovery are uncertain, but it has been suggested that recovery may be linked to the purported "Golden Age" of Roman Britain in the third and fourth centuries. The archaeological evidence for trade with, or raids on, Roman Britain is strongest in northern Leinster, centred on modern County Dublin, followed by the coast of County Antrim.

220 High King of Ireland

The High Kings of Ireland (Irish: Ard Rí na hÉireann) were sometimes historical and sometimes legendary figures who had, or who are claimed to have had, lordship over the whole of Ireland. Cormac mac Airt (son of Art), also known as Cormac ua Cuinn (grandson of Conn) or Cormac Ulfada (long beard), was, according to medieval Irish legend and historical tradition, a High King of Ireland. He is probably the most famous of the ancient High Kings, and may have been an authentic historical figure, although many legends have attached themselves to him, and his reign is variously dated as early as the 2nd century and as late as the 4th. He is said to have ruled from Tara, the seat of the High Kings of Ireland, for forty years, and under his rule Tara flourished. He was famous for his wise, true, and generous judgments.

140 Eblana Civitas

Eblana is the name of an ancient Irish settlement which appears in the Geographia of Claudius Ptolemaeus (Ptolemy), the Greek astronomer and cartographer, around the year 140 AD. It was traditionally believed by scholars to refer to the same site as the modern city of Dublin. There is no definitive proof to tie Eblana with any location, however, so its exact identity is still a matter of speculation. Early Irish antiquarians believed that the name Eblana in Ptolemy's Geographia was in fact a corruption of Deblana, itself a version of the Gaelic name Dubh Linn (Black Pool), from which the modern English language name Dublin derives. This seems not to be the only instance where Ptolemy truncated the initial letters of place names. For example, instead of Pepiacum, and Pepidii (in Wales), Ptolemy writes Epiacum and Epidii; and for Dulcinium (now Ulcinj, in Montenegro), he has Ulcinium.