Re-released in 1965 as "The End of the World" but only appeared as such in a few theaters, mostly in the Los Angeles area (Source: The American Film Institute Catalog of Motion Pictures). Was released under the original title thereafter.
When the family is in the car at the beginning of the film and suspect something is happening, they cannot pick up any "CONELRAD" stations on the car's radio. CONELRAD (COntrol of ELectromagnetic RAdiation), established in 1951, was the first nationwide system for emergency broadcasts in the United States. All radios made between 1953 and 1963 were required to have marks on the AM dial at 640 and 1240 MHz where citizens were expected to tune to obtain civil defense information. CONELRAD was succeeded by the Emergency Broadcast System in 1963 (which did not use dedicated frequencies) and it, in turn, was replaced by the Emergency Alert System in 1997.