Very interesting, I've never encountered these two before. What is their history? Mí na Súl Buí literally means "month of the yellow eye" - am I correct? Is it because July is usually the sunniest month of the year?
Also, what is Féile Eoin in this case?

24 June
Lá Fhéile Eoin = St John’s Day, Nativity of St John the Baptist.

In Conamara it's Lá (fhéile) tSin Seáin.
And on the eve of that day (Oíche Fhéil' tSin Seáin) it is traditional to burn bonfires.

http://tuairisc.ie/anocht-oiche-shin-se ... cumhachta/

Mí na Súl Buí = the month of the yellow eyes.
Actually I don't know if it's really about eyes or something else (súil is a cognate of Latin "sol" = sun...)

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

Thanks a lot for your explanatinons! I love learning about history and etymology.

Part of the reason for there being so many variations is that the Gaels did not traditionally have names for the months, per se, or so I've read (I thought I had a good article about it, but can't find it right now). They apparently described parts of the year (not necessarily distinct months) by characteristics or special times which occurred then. For example, the Scottish name for December, An Dubhlachd, referred originally to the dark period of the year, and not necessarily just that month.

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I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.