from gores profile,

Hundreds of years ago in what is now Great Britain and Northern France, lived the Celts.
i think that should be,

Thousands of years ago in what is now Great Britain, Northern France and Ireland, lived the Celts.

Newgrange has been since around 3200BC so it's older than the pyramids in egypt, and stonehenge in england.

and ireland is not part of great britain. ireland wasn't invaded by the english until 1200AD approx. there were lots of other invasions, like by the scots and normans. my history isn't at all good so i'm not sure exactly from when to when ireland would have been considered part of great britain.

but it's not now, and it wouldn't have been when people started celebrated the first of november, or chéad lá de mh* samhain.

samhain / m* na samhna means november / month of november as gaeilge. it also would mean hallowe'en, like oiche samhain, hallowe'en night.

lena chois an anuas, chun na firinne a rá, is doigh liom gur nach raibh alán eloais agat faoi na ruda* a scr*obh tu isteach sa do leathaghaidh, maidar le samhain.