Words for year in Celtic languages.

Proto-Celtic	*blēdanī / *bleido = year *ɸeruti = last year *se-blidnī = this year
Old Irish (Goídelc)	blíadaín = year uraid [ˈurəðʲ], urid, innurid = last year
Irish (Gaeilge)	bliain [bʲlʲiənʲ] = year anuraidh [əˈn̪ˠɔɾˠə] = last year i mbliana = this year an bhliain seo chugainn = next year athbliain / An Bhliain Nua/Úr = (the) New Year
Scottish Gaelic (Gàidhlig)	bliadhna [bliən̪ˠə] = year, vintage an-uiridh [ˈurəðʲ] = last year am bliadhna [əm’bliən̪ˠə] = this year (an) athbhliadhna [(ə’n̪ˠ)aflɪn̪ʲ] = next year athbliain / A’ Bhliadhna Ùr = (the) New Year
Manx (Gaelg)	blein [blʲeːnʲ / blʲiᵈn] = year, twelvemonth nurree = last year mleeaney = this year yn vlein ry heet, yn vlein shoh çheet = next year Nollick Veg, Yn Vlein Noa = New Year
Old Welsh	bloidin = year
Welsh (Cymraeg)	blwyddyn [ˈblʊɨ̯ðɨ̞n / ˈblʊi̯ðɪn] = year, a long time, ages; lifetime, life blwydd [bluːɨ̯ð / blʊi̯ð] = year (of age), twelve months (old), birthday, yearling llynedd [ˈɬənɛð] = last year eleni [ɛˈlɛnɪ / ɛˈleːni] = this year blwyddyn nesaf = next year blwyddyn Newydd = New Year
Old Cornish	bliþen = year
Cornish (Kernewek)	bledhen = year bloodh = year (of age) warlena / warleni = last year hevlena / hevleni = this year nessa bledhen = next year Bledhen Nowydh = New Year
Breton (Brezhoneg)	bloavezh = year ar bloaz a zeu = last year hevlene = this year ar bloaz tremen(et) / paseet = next year kala-bloaz = New Year

Etymology (year): possibly from the Proto-Indo-European *bʰloyd- (pale) [source].

Etymology (last year – Goidelic languages): from the Proto-Indo-European *péruti (last year) [source].

Words marked with a * are reconstructions.

Athbhliain faoi mhaise duit, Bliadhna mhath ùr, Blein Vie Noa, Blwyddyn newydd dda, Bledhen Nowydh Da, Bloavezh mat, Happy New Year!

Sources: Wiktionary, Am Faclair Beag, Online Manx Dictionary, Teanglann.ie, Geiriadur Prifysgol Cymru, Gerlyver Kernewek