Schedule is gate arrival time.
Then you have arrival into Newark which depending if it is landing North or South can probably be around a 10 minute difference.
Then add another 10 minutes for speed control on the arrival into EWR or even longer when they have to hold due to congestion. EWR is really bad in regards to congestion sometimes.
Flying around the jet stream can make the routes much more or much less favorable.
And most of the time this flight seems to after a flight time of 7 to 8 hours.
That’s not that much variation, is it?
Seems there is some buffer of maybe 30 minutes built into that gate arrival time so.
Could also be that the last 30 days or so, most of the time you could get routes around the jet stream leading to shorter flight times.
But the schedule needs to accommodate a wide window of flight times if United wants good on time statistics.
(United plans bigger buffers to have nicer statistics i believe)