If, by 'EU citizen', you mean that your spouse is non-Irish, then you can apply for naturalisation only after 5 years' reckonable residency. 'Reckonable residency' is calculated exclusively by GNIB stamps in your passport and does not, for instance, include any time spent on a student visa. What's more, you must have been resident for the entire year immediately preceding your application. Download the pdf from this site for further details:
http://www.inis.gov.ie/en/INIS/Pages/WP07000044
So in your case, you can only apply approximately 18 months from now--do bear in mind, though, that anecdotal evidence suggests that processing times for naturalisation run well over the 23-month average given by the INIS. So expect to have been in Ireland for up to (and perhaps even longer than) 8 years before becoming a naturalised Irish citizen.
