Can I enter the USA several hours before my I-20's earliest admission date?

[KevinLi]

My I-20 says the earliest admission date is 28th July, but my flight
will arrive in the USA at about 1:00 pm 27 JULY, so it is several hours
before the earliest admission date.
Will my entry be rejected? Can I wait at the airport until 0:00 am 28th July and
then start my entry?

[fuzzylogician]

I doubt they’ll let you in early. Depending on the airport it may be possible to just wait there for a few hours and then go through, but some (actually, many) airports won’t really have a place for you to sit for that long. I’d bet it will work out, but there are definitely ways that you could get in trouble and I don’t think anyone here can make you any promises. 

[TakeruK]

Is there any reason you have to arrive on July 27? If not, might be better to book the flight for 28th or later (or if it's already booked, paying the change fee is probably worth not having to wait in the airport for a day and/or the potential problems below).

By the way, most airports will not have their customs/passport control areas open 24 hours per day and like fuzzy said, most US airports that take international flights are set up to quickly funnel people from the gate to passport control. There are washrooms in between but often no food, seating and security are present to ensure people keep moving and don't try to sneak away. Typically passport control opens around 5am or 6am so if it's not open at midnight, you're going to be in this limbo for almost 11-16 hours. 

You could try to enter early and see what happens. They might allow you to stay and wait since there's nowhere you can go. Or, they might deny you entry and force you to return home. Also, your airline may not let you board the flight either. When an airline takes someone who is inadmissible to the USA, they are fined and forced to take the passenger back home. So, many airlines carefully check to ensure you are able to enter the USA before they let you board the flight. This check happens at the airport when you check in, typically, and I've heard stories where people confirm things with the airline ahead of time but then they are denied at the airport.

Unless there is a really compelling reason to enter on July 27 instead of July 28, I think it's a much better idea to book the flight or change the flight to a later date.