The Irish calendar does not observe the astronomical seasons (beginning, in the Northern Hemisphere, on the equinoxes and solstices), or the meteorological seasons (beginning on March 1, June 1, September 1 and December 1), but rather follows the seasons of the ancient Celts (see below) which are pre-Christian in origin. This is particularly evident in the Irish naming of many of the months: some names, like May (Bealtaine), August (Lughnasadh)/Lúnasa) and November (Samhain, sometimes also in the form of Mí na Samhna) were the names of pagan Celtic festivals. In addition, the names for September and October (Meán Fómhair and Deireadh Fómhair respectively) translate directly as "middle of autumn" and "end of autumn". Christianity has also left its mark on the Irish months: December is Mí na Nollag, or just Nollaig, the latter word also meaning Christmastide.
January - Eanáir
January 1 - New Year's Day, one of the Public Holidays in the Republic of Ireland.
- 1871 - disestablishment of Church of Ireland takes effect
- 1926 - 2RN (original radio station of present RTÉ) set up
- 1973 - Ireland becomes a member of the EU.
- 1975 - Ireland assumes first Presidency of the Council of the European Union (see July 1)
- 1984 - Galway City begins year long celebration of 500th anniversity (quincentennial) of mayoral status with Festival Eucharist in St. Nicholas' Collegiate Church
- 1990 - Ireland assumes fourth Presidency of Council of the European Union
- 2002 - Euro replaces punt as Irish currency
- 2004 - Ireland assumes sixth Presidency of the Council of the European Union
- January 2 - St. Munchin , Patron of the Diocese of Limerick
- January 3 - 1946: execution of William Joyce, Lord Haw-Haw
- January 5 - Twelfth Night
- January 6 - Little Christmas (Nollaig Bheag) and/or Women's Christmas (Nollaig na mBan)
- January 7 - 1922: Anglo-Irish Treaty ratified by Dáil Éireann
- January 8 - 1979: Whiddy Island disaster in Bantry Bay
- January 13 - 1941: death of James Joyce
- January 14 - 1965: Sean Lemass, Taoiseach, visits Prime Minister of Northern Ireland, Terence O'Neill
- January 16 - 1922: Michael Collins accepts surrender of Dublin Castle from the Viceroy, Lord Fitzalan
- January 17 - 1860: birth of Douglas Hyde
- January 20 -1968: death of Sir Alfred Chester Beatty
- January 21 - 1919: Meeting of the First Dáil in the Mansion House, Dublin
- January 22 - 1971: Ireland signs Treaty of Accession to EEC in Brussels
- January 27 - 1967: Northern Ireland Civil Rights Association founded
- January 28 - 1939: death of William Butler Yeats
- January 30 - 1808 work begins on Nelson's Pillar, Dublin.
- January 31 - St. Aidan, Patron of the Diocese of Ferns
Spring(February, March and April)
February - Feabhra
- February 1 - Imbolc, Feast of St. Brigid (Secondary Patron of Ireland) and Lá Feabhra, the first day of Spring
- February 2 - Candlemas
- February 3 - feast of Saint Blaise
February 6 - Feast of St. Mel , patron of the Diocese of Ardagh
- 1971 - first British soldier kiiled in Belfast
- February 13 - 1893: Gladstone introduces second Home Rule bill
- February 14 - St. Valentine's Day (relics of St. Valentine held inWhitefriar Street Carmelite Church in Dublin.
- February 15 - 1971: Decimal Day- Ireland abandons £sd.
February 18 - 1948: John A. Costello becomes Taoiseach
- 1982 - first of two General Elections in Republic this year (see 24 Nov.)
- February 19 - 1366: Statutes of Kilkenny promulgated
- February 24 - 1582: Bull of Pope Gregory XIII, for reform of calendar, issued at Rome
March - Márta
- March 1 - 1981: Bobby Sands begins hunger strike in Maze Prison
- March 3 - Charter of Trinity College, Dublin granted.
- March 5 - Feast of St. Kieran , patron of the Diocese of Ossory
- March 6 - 1152: Synod of Kells convenes.
- March 7 - 1848: first unveiling of the Irish tricolour (in Waterford).
- March 8 - 1966: Nelson's Pillar destoyed in explosion
- March 9 - 1932: Eamon de Valera elected President of the Executive Council of the Irish Free State
- March 10 - 1894: Ireland wins Rugby Triple Crown for first time
- March 13 - 1979: Ireland joins new European Monetary System (EMS)
- March 17 - Saint Patrick's Day (public holiday), and for Irish Roman Catholics, a Holy Day of Obligation
- March 18 - 1899: Ireland wins Rugby Triple Crown for 2nd time
- March 21 - 1978 death of Cearbhall Ó Dálaigh former President of Ireland
- March 23 - 1971: Brian Faulkner elected PM of Northern Ireland
- March 24 - Feast of St. Macartan , patron of the Diocese of Clogher
- March 29 - 1859: first issue of The Irish Times
- March 25 - One of the four Irish Quarter days
- March 29 - 2004: Smoking ban in all work places introduced in Ireland
- March 30 - 1979: Ireland announces ending of one-for-one parity with sterling.
April - Aibreán
- April 1 - April Fool's Day - Lá na nAmadáin
- April - 1914: Cumann na mBan founded
- April 4 - 1774: death of Oliver Goldsmith
- April 8 - Gladstone introduces first Home Rule bill.
- April 10 - 1966: Commemoration of 50th anniversary of Easter Rising begins
- April 11 - 1951: Dr Noel Browne, resigns as Minister for Health over "mother-and-child" controversy
- April 13 - 1742: world premiere of Handels Messiah in Dublin
- April 16 - 1871: birth of John Millington Synge
- April 17 - 1783: British Renunciation Act recognises Irish legislative independence
- April 18 - Feast of St Laserian , patron of Leighlin Diocese of Kildare and Leighlin .
- April 19 - 1875: Charles Stewart Parnell elected MP for Meath
- April 20 - 1912: death of Bram Stoker
- April 21 - 1916: Roger Casement lands at Banna Strand
- April 23 - 1014: Battle of Clontarf and death of Brian Boru, High King of Ireland on Good Friday
- April 24 - 1916: Start of the Easter Rising.
- April 28 - 1958: Aer Lingus service to North America inaugurated
- April 29 - 1916: Easter Rising ends with surrender
- April 30 - 1994: First performance of Riverdance at Eurovision Song Contest
Summer(May, June and July)
May - Bealtaine
The first Monday in May is a public holiday.
- May 1 - Beltane and Lá Bealtaine, the first day of Summer
- May 2 - 1872: St. Patrick's Cathedral, Dublin, becomes the National Cathedral of the Church of Ireland
- May 3 - Feast of St Conleth , patron of Kildare Diocese of Kildare and Leighlin
- May 5 - 1949: Ireland one of ten founder members of Council of Europe with HQ is Strasbourg
- May 6 - 1074: death of Dúnán , first bishop of Dublin
May 7 - 1915: Lusitania sunk off Old Head of Kinsale
- 1931 - An Óige (Irish Youth Hostel Association ) founded
- May 11 - 1967: Ireland applies to join EEC
- May 13 - 653 (Pentecost Sunday): Monastery founded on Iona by Saint Columcille
- May 14 - Feast of St. Carthage , patron of Lismore Diocese of Waterford and Lismore
- May 15 - 1847: death of Daniel O'Connell at Genoa
- May 16 - Feast of Saint Brendan, patron of the Diocese of Clonfert
- May 19 - 1870: Home Rule movement founded by Isaac Butt in Dublin.
- May 21 - 1799: Bill of Union (later the Act of Union) introduced in Irish House of Commons
- May 24 - 1487: Lambert Simnel crowned "Edward VI of England" in Dublin.
- May 25 - 1914: Third Home Rule bill passed by British Parliament
- May 26 - 1972: Special Criminal Court established in RoI
- May 30 - 1941: Enactment of Second Amendment of the Constitution Act .
- May 31 - 1941: Luftwaffe bombs Dublin
June - Meitheamh
The first Monday in June is a public holiday.
- June 3 - Feast of St. Kevin (Abbot of Glendalough) and patron of the Archdiocese of Dublin ,
- June 4 - 1798: death of Lord Edward Fitzgerald
- June 6 - Feast of St. Jarlath patron of the Archdiocese of Tuam
- June 7 - 1921: first meeting of House of Commons of Northern Ireland
- June 8 - First Home Rule bill defeated
- June 9 - Feast of Saint Columcille (Secondary Patron of Ireland)
- June 10 - 1642: first rgularly constituted presbytery meets in Carrickfergus.
- June 13 - 1713: Jonathan Swift installed as Dean of St. Patrick's Cathedral, Dublin
- June 14 - 1939: Offences Against the State Act passed
- June 16 - Bloomsday
- June 16 - 1922: Elections held for Third Dáil
- June 18 - 1541: Henry VIII declared King of Ireland by Irish Parliament.
- June 20 - 1763: birth of Wolfe Tone
- June 22 - 1866: creation of first Irish Cardinal, Archbishop Paul Cullen of Dublin.
- June 23 - St. John's Eve / Bonfire Night
- June 24 - One of the four Irish Quarter days
June 25 - 1731: Royal Dublin Society founded.
- 1891 - Charles Stewart Parnell marries Kitty O'Shea
- 1938 - Douglas Hyde inaugurated as President of Ireland
- 1945 - Seán T. O'Kelly inaugurated as President of Ireland
- 1952 - Seán T. O'Kelly inaugurated for second term as President of Ireland.
- 1959 - Eamon de Valera inaugurated as President of Ireland.
- 1966 - Eamon de Valera inaugurated for second term as President of Ireland.
- 1970 - Roman Catholic bishops announce end of ban on RC attendance at Trinity College, Dublin
- 1973 - Erskine Childers inaugurated as President of Ireland.
- June 26 - 1963: John F. Kennedy begins state visit to Ireland
- June 29 - 1315: Edward Bruce inaugurated as High King of Ireland
July - Iúil
- July 1 - 1937: Constitution of Ireland (Bunreacht na hÉireann), enacted by plebiscite.
- July 6 - 1907: theft of Irish Crown Jewels from Dublin Castle discovered
- July 8 - 689: Martyrdom of St Kilian at Würzburg
- July 10 - 1931: assassination of Kevin O'Higgins Minister for Justice
- July 11 - Feast of St Oliver Plunket
- July 12 - a public holiday in Northern Ireland
- July 15 - 1948: An Taisce , the National Trust for Ireland, set up
- July 18 - 1872 introduction of the secret ballot
- July 21 - 1976: assassination of Christopher Ewart-Biggs British ambassador to Ireland
- July 23 - 1693: death of Patrick Sarsfield, at Battle of Landen
- July 24 - Feast of St. Declan
- July 26 - 1856: birth of George Bernard Shaw
- July 31 - 1917: death of Francis Ledwidge
- Garland Sunday (last Sunday of month)
Autumn(August, September and October)
August - Lúnasa
The first Monday in August is a public holiday.
- August 1 - Lughnasadh/Lá Lúnasa, the first day of Autumn
- August 2 - 1799: pre-union Irish Parliament meets for last time
- August 5 - 1847: funeral in Dublin of Daniel O'Connell
- August 8 - 1923: Act to establish Garda Síochána passed
- August 9 - Feast of St. Felim and St. Nathy
- August 10 - 1636: compilation of the Annals of the Four Masters completed.
- August 11 - 1927: Fianna Fáil TDs take seats in Dáil Éireann
- August 12 - 1922: death of Arthur Griffith
- August 14 - 1903: Wyndham Land Act passed
- August 15 - Feast of The Assumption of Mary
- August 16 - 1921: First meeting of Second Dáil
- August 19 - 1504: Battle of Knockdoe
- August 21 - 1970: Social Democratic and Labour Party-SDLP founded
- August 26 - 1921: Eamon de Valera elected President of the Irish Republic
- August 22 - 1922: death of Michael Collins
- August 23 - 1170: Richard de Clare, Strongbow, lands near Waterford.
- August 25 - 1170: Strongbow marries Aoife , daughter of Diarmuid MacMorrough the King of Leinster .
- August 27 - 1979: Lord Mountbatten killed in IRA assassination in County Sligo
- August 29 - 1890: National Museum of Ireland and National Gallery of Ireland opened.
- August 30 - Feast of St. Fiacre (Fiachra)
September - Meán Fómhair
- September 1 - 1737: first issue of Belfast News Letter .
- September 2 - 1939: Enactment of First Amendment Amendment of the Constitution Act .
- September 4 - 1607: the Flight of the Earls.
- September 5 - 1931: first issue of The Irish Press newspaper
- September 7 - 1948: John A. Costello announces his intention of declaring Ireland a republic in Ottawa
- September 9 - Feast of St. Kieran of Clonmacnoise
- September 10 - 1923: Irish Free State joins League of Nations
- September 11 - Drogheda captured by Cromwell
- September 14 - Feast of the Exaltation of the Holy Cross (the following Wednesday, Friday and Saturday were observed as Quarter tense)
- September 16 - 1961: Hurricane Debbie hits Ireland.
- September 18 - 1914: Third Home Rule bill receives Royal Assent but its implementation is suspended.
- September 20 - 1803: death of Robert Emmet
- September 25 - Feast of St. Finbarr
- September 26 - Eamon de Valera makes inaugural speech as Chairman of the League of Nations
- September 28 - 1484: creation of the Wardenship of Galway
- September 29 - One of the four Irish Quarter days
October - Deireadh Fómhair
The last Monday in October is a public holiday.
- October 3 - 1691: Treaty of Limerick signed.
- October 5 - 1582: as a consequence of the introduction of the Gregorian calendar, Oct.5, - Oct.14, not included in calendar for 1582
- October 6 - 1175: Treaty of Windsor signed
- October 11 - Feast of St. Canice
- October 14 - 1882: birth of Eamon de Valera
- October 16 - Feast of St. Gall
- October 19 - 1745: death of Jonathan Swift
- October 22 - 1976: Cearbhall Ó Dálaigh resigns as President of Ireland.
- October 25 - 1920: Terence MacSwiney , Lord Mayor of Cork , dies on 74th day of hunger strike
- October 29 - Feast of St. Colman of Kilmacduagh
- October 31 - Halloween/Samhain/Oíche Shamhna
Winter (start)(November, December and January see above)
November - Samhain / Mí na Samhna
- November 1 - All Saints Day and Lá Samhna (November Day), the first day of Winter
- November 2 - 1950: death of George Bernard Shaw
- November 3 - 1796 first court sittings at the Four Courts, Dublin
- November 6 - Feast of All the Saints of Ireland
- November 7 - 1791: The Custom House, Dublin, opened
- November 8 - 1847: birth of Bram Stoker
- November 10 - 1728: birth of Oliver Goldsmith
- November 11 - 1933: Abolition of appeal from courts of the Irish Free State to the Privy Council.
- November 16 - 1965: death of W.T. Cosgrave, first President of the Executive Council of the Irish Free State
- November 17 - 1974: death in office of Erskine Childers, President of Ireland.
- November 19 - 1798: death of Wolfe Tone
- November 21 - 1921: Bloody Sunday in Dublin
- November 24 - 1982: second General Election in Republic this year (see Feb. 18)
- November 25 - 1913: Irish Volunteers founded
- November 30 - 1667: birth of Jonathan Swift
December - Nollaig / Mí na Nollag
- December 1 - 1494: Poynings Law enacted
- December 3 - 1976: Patrick Hillery inaugurated as President of Ireland.
- December 6 - Feast of Saint Nicholas, chief patron of the City of Galway
- December 8 - Feast of the Immaculate Conception, for Irish Roman Catholics, a Holy Day of Obligation
- December 9 - 1922: First meeting of the first Senate of the Irish Free State
- December 11 - 1921 Sack of Cork by Black and Tans
- December 12 - 1936: Abdication of Edward VIII recognised in the Irish Free State by the enactment of the Executive Authority (External Relations) Act, 1936
- December 13 - Feast of Saint Lucy (the following Wednesday, Friday and Saturday were observed as Quarter tense)
- December 14 - 1955: Ireland admitted to UN
- December 17 - 1834: opening of the first Irish railway - the Dublin Kingstown Railway
- December 18 - Feast of St. Flannan patron of the Diocese of Killaloe
- December 19 - 1974: Cearbhall Ó Dálaigh inaugurated as President of Ireland.
- December 22 - 1989: death of Samuel Beckett, Saoi of Aosdána
- December 23 - 1920: Government of Ireland Act passed
December 25 - Christmas Day (Public Holiday), one of the four Irish Quarter days
- for Irish Roman Catholics, a Holy Day of Obligation
- December 26 - St. Stephen's Day (Public Holiday)
- December 29 - 1937: Constitution of Ireland comes into operation.
Calendar terms in Irish language
Days of the week - Laethanta na Seachtaine
- Monday: Dé Luain
- Tuesday: Dé Máirt
- Wednesday: Dé Céadaoin
- Thursday: Déardaoin
- Friday: Dé hAoine
- Saturday: Dé Satharn
- Sunday: Dé Domhnaigh.
Seasons of the year - Ráithí na Bliana/Na Séasúir
- Spring: An tEarrach - Spring/Vernal Equinox: Lá Leathach an Earraigh
- Summer: An Samhradh - Summer Solstice: Grianstad an tSamhraidh
- Autumn: An Fómhar - Autumnal Equinox: Lá Leathach an Fhómhair
- Winter: An Gheimhreadh - Winter Solstice: Grianstad an Gheimhridh
Religious seasons - Séasúir Creidimh
- Lent: An Carghas
- Easter: Cáisc
- Advent: An Aidbhint
- Christmastide: Nollaig
- Quarter Tense: Laethanta na gCeithre Thráth
Holidays and holydays - Féilte na Bliana
- Holiday: Lá Saoire
- Public Holiday: Saoire Poiblí
- Church Holyday: Lá Saoire Eaglaise
- New Year's Eve: Oíche Chinn Bhliana
- New Year's Day: Lá Caille
- Epiphany: Nollaig Bheag or Nollaig na mBan
- St. Brigid's Day: Lá Fhéile Bríde or Lá Feabhra
- St. Patrick's Day: Lá Fhéile Phádraig
- April Fools Day: Lá na nAmadáin
- Annunciation: Lá Fhéile Muire san Earrach or Lá Theachtaireacht an Aingil
- May Day: Lá Bealtaine
- Assumption: Lá Fhéile Muire san Fhómhar
- Hallowe'en: Oíche Shamhna
- 1 Nov: Lá Samhna
- All Souls Day: Lá na Marbh
- Immaculate Conception: Giniúint Mhuire gan Smál
- Christmas Day: Lá Nollag
- St. Stephen's Day: Lá Fhéile Stiofáin or Lá an Dreoilín
Movable feasts - Na Féilte Reatha
- Advent: An Aidbhint
- Shrove Tuesday: Máirt na hInide
- Ash Wednesday: Céadaoin an Luaithrigh
- Lent: An Carghas
- Holy Week: Seachtain na Páise
- Palm Sunday: Domhnach na Pailme or Domhnach na hImrime
- Spy Wednesday: Céadaoin an Bhraith
- Holy (Maundy) Thursday: Déardaoin Mandála
- Good Friday: Aoine an Chéasta
- Easter Sunday: Domhnach Cásca
- Easter Monday: Luan Cásca
- Ascension Thursday: Déardaoin Deascabhála
- Corpus Christi: Déardaoin Chorp Chríost
- Pentecost Sunday: Domhnach Cincíse
- Whit Monday: Luan Cincíse