Unless you have TSA-precheck or other program to expedite the security line process, it is good to allow 2 hours in EWR or perhaps a bit more if you are checking a bag. (You can see estimated wait times here: https://www.tsawaittimes.com/security-wait-times/EWR/Newark-International)
Train schedule for Thursday/Friday https://www.njtransit.com/train-to?origin=Princeton%20Station&destination=EWR%20Newark%20Airport%20Station&date=06%2F02%2F2022
Depart Princeton at 12:50, 13:11, 13:46, 14:13, 14:47, 15:16, 15:38, 16:14, 16:38, 17:06, 17:30, 18:10, 18:33, 19:15, 19:58, etc..
Schedule for Saturday https://www.njtransit.com/train-to?origin=Princeton%20Station&destination=EWR%20Newark%20Airport%20Station&date=06%2F04%2F2022
As you saw coming, the train takes about 1 hour (+/- 5 minutes) plus the time for the airport train to the terminal itself. Taking an über to the Princeton Junction station can save the walk to the train station
An Uber all the way the airport is likely $80 (or $100 for a large car) - can be a cost effective solution in groups.. Time via car is also about 1 hour. (+traffic..)
Find out your train status here https://www.njtransit.com/dv-to/Princeton%20Junction%20Station
