Q. My movie takes place over a 24 hour period, with most scenes in one of two main locations. There are a couple of points when I want to make clear that significant time has passed since the previous scene, which was in the same location. To solve this, my cinematographer/cameraman and I have decided to put a large clock in the room and we can cut to it at the beginning of the new, later scene.
The question I have is, should I reference the clock in the script or is that a detail just for the shooting script?
Anything you need the audience to see had better be in the script, whether you're shooting it or trying to sell it.
But I wouldn't go with a clock. If all you need to do is tell time, I'd just put a time stamp on the screen directly. It feels like clumsy. The audience is used to time subtitles -- HEROES is full of them, so is THE WEST WING, and others too numerous to mention.
If you want to be cleverer, work it into dialog. Or give us specific clues that tell us how much time has passed that aren't so on the nose. Table set for dinner. Food on table. Dirty plates on the dining table. Sun in the eastern window, sunset in the western window. Night. The party upstairs. Silence from upstairs. Changes of clothes. Have someone spill wine on his white shirt; if we see the stain, we know it's later.
In other words, try to make the time crystal clear by showing, not telling us. A clock is telling us. Giving us clues we can easily interpret for ourselves is showing. We like to figure things out for ourselves, so give us a chance.