I remember only a brief scene from this episode/movie. The scene was in black and white. The main character was a soldier who had gone back in time, actually meeting himself as a kid. This soldier was hiding in bushes, or the kid showed him a hiding place under the front porch of a house and was spying on a group of aliens.
The aliens (Martians?) had 3 all black eyes and were dressed like Men in Black with suits, fedoras, and trench coats. The aliens may have been searching for the soldier. As he was observing them they were greeting someone, or making a deal. The aliens were also driving late 50's or early 60's black sedans.
The soldier was Caucasian, blond? Curly hair, had a beard? His uniform was a mix of old and new, modern (green? solid color)M65 field jacket and WW2 German leather suspenders. He had a Kennedy half dollar that he gave to his younger self, which is how he realized the kid was himself as a boy.
I am thinking that this may have been an outer limits episode.