The length of the key changes several times.
If the space mission spoken of in the film is the Apollo 11 mission, then the launch date should have been July 16, not July 20.
In the film, a small tremor occurs before a major earthquake. Usually this should happen in reverse, even in an area of high seismic activity such as Japan.
Although the cameraman is always filming the action while the red LED that indicates that the camera is recording is never turned on, this is probably a conscious decision by director Satoshi Kon as the 'recorded' scenes are fictional even within the context of the movie.
In the Japanese Version, the news indicates that the astronauts of the Apollo 11 mission departed from Cape Canaveral in 1969. During the Apollo missions, the name was Cape Kennedy. The name of Cape Canaveral, was re-registered until 1974.
The early Chiyoko's films (according to history during the late 30s and early 40s) are made in color, but Carmen Comes Home, the first color feature film in Japan, using Fujicolor, was made in 1951.