Hi. I've been interested in learning Irish for quite a while now, and recently started dabbling in it again. I figured learning calendar day/month names in Gaeilge would be a good little start. ;)

I've noticed some confusion in regards to spelling, though.. I'll list the ways I've seen them below.

Sunday - Domhnach, Dé Domhnaigh
Monday - Luan, Dé Luain
Tuesday - Máirt, Dé Máirt
Wednesday - Céadaoin, Dé Céadaoin
Thursday - Déardaoin, Dé Déardaoin
Friday - Aoine, Dé hAoine
Saturday - Satharn, Dé Sathairn

If someone could explain this to me, I'd be grateful. Thanks.

An Domhnach - Sunday

Dé Domhnaigh - On Sunday

So then a THIRD one? All of the first ones I listed with An in front?

The Gaeilge for "Monday" is "An Luan", as opposed to just "Luan", as is with all the days.

Nouns come in different cases, eg.

Ireland :: Éire
The People of Ireland :: Muintir na hÉireann
To Ireland :: go hÉirinn

The word "Dé" is a preposition which is unique to days. It means "on the", like "ar an":

Chonaic mé é Dé Domhnaigh.
I saw him on Sunday.

Chonaic mé é ar an Luan. (Luain?)
I saw him on Monday.

I've no idea what case follows "Dé", but if I'd to guess I'd say it's the Dative, just like any other preposition.

Usually, I'd go to An Foclóir Beag and check the cases, but it's down at the moment.

I know it seems strange that there's a unique Dative for so many days... all I can say is that it's not the Genetive, because as far as I know, the genetive of "Máirt" is "Máirte", so you have:

An Mháirt
Dé Máirt
Maidin na Máirte

An Domhnach
Dé Domhnaigh
Maidin an Domhnaigh (?)

I suggest, when An Foclóir Beag is back up and running, that you go and check the cases.

Wow. Heh. I *really* wanna learn Irish, but it seems *so* impossible, especially when I read stuff like you just said. :P

Off topic, I was meandering through the internet last night, looking up stuff on Gaeilge, and came across Shelta; I never had before.

It seems both intriguing and silly at the same time; I only wish I was a traveller so I could learn it in full. ;)

Fear na mBróg has it slightly wrong, I think.

Chonaic mé Dé Luain é
I saw him on Monday

Chonaic mé é ar an Luan ina dhiaidh sin
I saw him on the Monday after that.

The Dé in some versions of the names of days comes from a previous version Dia = God, from the latin "Dies"

The names of weekdays are (mostly) taken from the names of planets, which in classical times were also the names of Gods. And so Dia/Dé doubles up as a synonym for Lá (Day) in the names of weekdays.

The weekday names used in Irish came mostly from Latin.

Luan = Luna, the moon
Máirt = Mars
Céadaoin = first fast day (original Irish name)
Déardaoin = Dé idir dhá aoin (day between two fasts)
Aoine = fast day
Satharn = Saturn
Domhnach = Dies Dominicae the Lord's Day

Compare english
Monday = Moon
Tuesday = Tyr, Norse equivalent of Mars, god of War
Wednesday = Woden, Norse father of Gods, but equated with Mercury
Thursday = Thor, Norse God of Thunder, equated therefore with Jupiter
Friday = Freya, equated with Venus
Saturday = Saturn
Sunday = What it says on the tin.

Hope this helps somewhat