As per here:
131 leaves Connolly at 11 AM, arrives in Maynooth at around quarter to 12, leaves for return to Connolly at 5 past 12, and arrives at 10 to 1.
Departs for a second trip from Connolly at 25 past 2, arrives again in Maynooth at 10 past 3, leaves at around half past 3, and finally arrives in Connolly at 2 past 4.