Hi Brad, welcome to SS.
As you're probably aware -
The Day & Night are usually reserved as a logistical factor for production but they also evoke for a reader.
Space never has a Day/Night, far as I know.
Alien screenplay, for example:
FADE IN
SOMETIME IN THE FUTURE:
INT. ENGINE ROOM
Empty, cavernous.
INT. ENGINE CUBICLE
Circular, jammed with instruments.
All of them idle.
Console chairs for two.
Empty.
INT. OILY CORRIDOR - "C" LEVEL
Long, dark.
Empty.
Turbos throbbing.
No other movement.
INT. CORRIDOR - "A" LEVEL
Long, empty.
For your Submarine heading - INT. SUBMARINE would do, imho, and you could do similar to above. Best keep in mind from a lighting perspective:
https://www.quora.com/Do-submarines-have-different-interior-lighting-for-day-and-nightApparently lights are different for day/night in a sub.
You might use a Super after description with where they are (what ocean) and the time perhaps?
Perhaps indicate looking at an internal clock 2300 Hours or write in a Super: Twenty-Three Hundred Hours.
Cutting to outside shots, (if you do) will indicate Day or Night.
As far as your windowless location, or Bank Vault, or mine shaft, cave, or train tunnel, I'd leave it off and only consider it if cutting same time to an outside location. If for example you cut to a rescue team in another location readying to pull someone out of that Cave it might be DAY, but it's always going to be lit the same way in the cave, so I wouldn't bother. I'd bother more with atmosphere.
In The Descent 2
INT. CRAWLSPACE - DARKNESS
Tight. Claustrophobic. The team wriggle on hands and knees as
the tunnel tapers ever tighter. Rock bears down above.
It's a good question.
But yes, it can be dropped and no rankling should result. :D