If you do buy a seat reservation, which can cost anything from £4 upwards, you'll be able to check-in from 60 days before departure.
In a short statement the airline said: "Online check-in (for those customers who don’t choose reserved seats) will be available from 48 hours to 2 hours pre-departure for all flights from Wednesday, 13th June."
This means you will have to find a place to print off your boarding pass whilst on holiday should you not have the Ryanair app on your iPhone or Android mobile phone.
Fail to do this and you will have to check-in at the airport where a fee of £55-per-person will be charged and the change applies to ALL flights from 13 June - both new bookings and existing reservations.
Ryanair also said that the available time is double the 24 hour check-in period operated by Aer Lingus, British Airways, Lufthansa, Norwegian and Iberia, although these airlines don't charge a fee for check-in at the airport. (via Norm at LFN Digestive)