What validity do I need on my Irish passport for overseas travel?
This depends on where you're travelling to.
Your Irish Passport must be valid up to your return date.
Your Irish Passport must be valid up to your return date. And you must also get an Electronic System for Travel Authorisation (ESTA) under the Visa Waiver Programme for entry into the United States. You can find more information on the US Embassy in Ireland's website.
All other countries
The passport validity required for countries outside of the European Union and the United States varies greatly so contact your travel agent or the embassy of the country you're travelling to for the most up-to-date requirements.