When Joe and Johnny leave in the morning for work and school, the sun is shining on their house from the left, judging by the shadows. When Joe returns home from work, the sun and the shadows are the same. Note the shadow of Joe's house on the one next door to the right in both scenes.
The movie seems to imply that the entire world is hearing "the voice" simultaneously. With the story evidently taking place on the west coast of the U.S., that would mean that European countries would actually be listening in the wee hours of the morning. Other countries in the Eastern Hemisphere would have to be tuned in well into the middle of a standard workday. This peculiarity is never addressed in the script.
Telephone booth on the tarmac.