This fare is available for departures starting early September through November, and travel is available daily, but you might have better luck searching for departures midweek.
Please take note that this is Aer Lingus' saver fare, which only includes a carry-on bag plus one personal item up to 22 lbs. Consider their smart fare at $445 round-trip if you need checked baggage allowance or would like to choose a specific seat.
Searching on the Aer Lingus website, I was able to find seats departing BOS on Saturday, October 20, and returning from SNN on Wednesday, October 31, 2018.
For all the Boston based travelers have a look at our BOS flight deals page for a full list of low prices we've found today.
Need a room in Ireland? Here's what's available for the mentioned dates on Hotelwatchdog.