Continuity mistake: Juror #4 announces the time to be 6:15, a couple of minutes later when Juror #3 is about to break down, tearing up the photo of himself with his son, his watch shows 5:10.
Continuity mistake: Early in the film, Henry Fonda and another juror are in the men's room. When the other juror exits, the door is a swinging door. From the jury room the door is a regular door with a door knob. You can hear the door close when Henry Fonda exits and closes the door.
Answer: He was actually talking about the night before the last one. Trials, especially longer ones for serious crimes such as murder, are not usually on consecutive days...often there is a recess after the prosecution rests, and another after the defense, before closing arguments and the jury's deliberation. During those recesses, unless they are sequestered, the jury members would return to their normal lives (including work), and report back to the court when summoned.