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.
Seasons
Winter (end)
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. Aiden, Patron of the Diocese of Ferns
Spring
(February, March and April)
February - Feabhra
March - Márta
The last days of March and the first three days of April are known as The Old Cows Days/The Days of the Brindled Cow or, in the Irish language, Laethanta an Bó Riabhaigh.
April - Aibreán
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.
July - Iúil
Autumn
(August, September and October)
August - Lúnasa
The first Monday in August is a public holiday.
September - Meán Fómhair
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
- 1871: Fenian invasion of Canada.
- 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
December - Nollaig / Mí na Nollag'
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