When Dr. Austin is explaining the effects of the Electro-Magnetic Pulse (EMP) from the nuclear blast, he says. "It's all theoretical. It's never happened before." In actuality, the United States detonated a 3.8 Megaton warhead at an altitude of 50 miles, 1 August 1958, in the Operation Hardtack Teak shot nuclear test. This event caused unexpected communications disruption and damage to electrical equipment in an area that ranged between Hawaii and New Zealand. It was the first observation of the EMP effect.
In the original broadcast of The Day After, one of the cast seems to be stifling a laugh. Specifically, when Willie is berating his fellow soldiers about waiting for military helicopters to relieve them of their post he makes the remark "So what are you here guarding? Some cotton pickin hole in the ground with nowhere to go?" In the original TV edit, it's clear that the actor Willie was talking to was stifling a laugh. Indeed, you can see a smile on his face just before the camera cuts away.
In the original TV release, while on the "looking glass" plane, the officer who is receiving the telephone information regarding the "the massive attack against the US at this time. ICBM's numerous ICBM's" is clearly smiling/smirking. Moments later, when he says "over three hundred missiles inbound now" he presents another smile/smirk.
When Denise Dahlberg runs outside after the attack and is chased by Stephen Klein, both are covered in what looks like ash very thoroughly, but both of them are clean once they get back inside the house.
When the rockets go off, Mrs. Hendry is at her dressing table in her pink robe. When she runs to the window, she is naked with only a sheet held up to her front. She sees the rockets, dashes from the window, and comes out the downstairs door in her pink robe again.
When Dr. Oakes is listening to the radio on the freeway, the interior shot shows that his car is in the right lane. In the next exterior shot, he is in the left lane and crosses the right to exit the freeway. There is also no traffic heading in the opposite direction at all.
The scene from the SAC Airborne Command Post where information about the incoming Soviet attack is being relayed shows an Air Force officer reporting, "Missile Warning, this is Beale: confidence is high; I repeat, confidence is high." Previously, in the scene where the Missile Combat Crew was discussing the U.S. ICBM launch, one of the officers had mentioned that the Soviets had already hit "two of our radar warning stations...Beale Air Force Base in California and somewhere in England." Beale could not have been sending the data if it had already been taken out.
In the opening scenes where Billy McCoy and his counterparts are discussing their upcoming plans while riding a helicopter to the base, the helicopter's shadow can be seen on the trees below. The shadow is that of a Bell 206 Jet Ranger, but when the camera cuts to an outside shot of the helicopter, it is actually a Bell UH-1N Huey.
The deputy silo-officer with the orange ascot wears the name "Krause" on his uniform, but after the missile launches, Billy McCoy and his comrades talk about the two men in the capsule of the Oscar Base as "Star and Boyle".
When Dr. Oakes first realizes he is the only one on I-70 heading into Kansas City and that everyone else is heading out, an exterior shot shows his car almost level with an offramp. Later, when the bombs hit, his car stalls near the same offramp.
The maintenance team flew into and out of Launch Control Facility Oscar 1. Oscar 1 is located on Whiteman AFB just to the south of the security police squadron and the maintenance shop. They could have walked to it.
Surely intentional by the director but the movie kept referring to Sedalia where Whiteman AFB is located. Sedalia is several miles East, the name of the small town where Whiteman is located is Knob Noster. However, the ICBMs at Whiteman were scattered around several hundred square miles adjacent to the base. In fact, several Minuteman II silos (specifically, Launch Facilities B-07, C-08, C-09, E-10, and E-11) were quite close to Sedalia.
Early in the movie, before the nuclear strikes, a young farmer pumps the handle of a yard hydrant to get a drink of water. This type of hydrant is used for a pressurized system and does not use a pump action. It is either on or off.
The uniforms the Air Force enlisted men are wearing are wrong. They are wearing "colored" Strategic Air Command patches on their right breast pocket when they should be subdued, none of the missile mechanics are wearing their missile maintenance badge, also known as a "pocket rocket" patch on their left breast pocket, and the two security policemen are not wearing their subdued police badge patches on their left breast pockets and have "SP" stenciled on their fatigue hats. Security policemen wear berets.
(at around 55 mins) Dr. Oakes' daughter and other people are shown being vaporized by the nuclear blasts, and screams are heard from the victims as they die. In reality, they would have in all likelihood been vaporized instantly, having no time to scream or otherwise react to the blast. In addition, the daughter's death is depicted as an awkward juxtaposition of a shots: the fist showing of the lower half of her body igniting, followed by a close-up shot of her being vaporized.
An all-out nuclear war is hypothesized by scientists to produce enough soot and fallout to completely blot out the sun, resulting in an extended nuclear winter around the Earth. The film depicts a brief nuclear snowfall soon after the bombing ceases, but for the rest of the film the landscape is mostly bathed in a hazy sunlight.
When Airman McCoy is talking to his wife at their house he tells her he will be "out of the service in 6 months". His rank is Airman First Class and at the very least, he would have a full year before his 4 year enlistment is over at his current rank.
The movie does not show a nuclear winter. However, the theory of nuclear winter was developed at about the same time that this movie was filmed, and only became known to the general public after The Day After was released.
In the establishing shot scene of the SAC Airborne Command aircraft, after the missile launches, the aircraft appears to be a KC-135 Stratotanker, due to the prominent aerial refueling boom under the tail. However, the EC-135 "Looking Glass" also had an aerial refueling boom. Following its mission, the EC-135 had the ability to refuel the next aircraft sent up to relieve the previous crew.
During the nuclear strike, the flag outside the Dahlberg farm is being blown by a breeze from the left side of the screen but the debris is blowing in from the right. However, this could mean that the wind was swirling.
When teenager daughter Denise runs amok in the farm
field after the nuclear attack, she lightly brushes up against a dead cow and moves the entire carcass, thus revealing it to be a lightweight stuffed prop.
The shock wave from one of the bombs is strong enough to flip over the semi trailer Billy McCoy is hiding in, but does no damage to any other vehicle around it, even though many have hoods and doors open which in all likelihood would be ripped off. There is also no debris in sight.
Dr. Oakes is driving at speed along I-70 towards Kansas City when the first bomb is air-burst over downtown. Subsequent exterior shots show that vehicles heading out of Kansas City were crossing over to the wrong side of the freeway in panic to get around the outbound gridlock before the EMP effect stalled them. However Dr. Oakes drives as if there were no other cars heading towards him the wrong way at speed.
In the calm immediately after the bombs are done falling, we see a collapsed house with the charred remains of a woman. Although her clothes and her skin have been carbonized by the heat of the bombs, her hair is completely intact and shows no signs of singeing or melting.
When they are putting dirt in the windows for the Dahlberg house, it shows that 3 people are doing it simultaneously. This could not happen. The young daughter and the son are in the basement with the water jugs, the mom is preparing for the wedding and the oldest daughter is somewhere else. The dad is the only one who is putting dirt in the windows yet it shows dirt being thrown on the windows at the same time.