1)  What do I write in a scene heading when the time is unknown, such as in a room with no windows, or an underground nuclear weapons facility?

2)  When I have the same location, but I skip time, how do I do it?  Such as when the protagonist starts writing a letter, to when he seals the envelope.  Do I write "Later" after an apostrophe, put it as the time, or other?

1/ In any location you must indicate the time, when there is a possibility to check it out (in a room without window you can get out). There are exception i.e. underground nuclear weapons facility, if the action is never going out, no need to indicate it, or when someone awakes in some place and doesn't know what time it is and there is no windows. This kind of scene are quite rare.

2/ you have several options. You can do a:

                               DISSOLVE TO:

or

                               TIME CUT:

and indicate i.e. EXT. HOUSE - NIGHT (LATER)

Michel

1) This is the first slugline of The Inside Man's script: 'INT. DALTON'S CELL - UNDETERMINED'

I've seen this in other scripts as well and I believe it'll work for the scene you want. You can also just write: 'INT. UNDERGROUND NUCLEAR FACILITY' without indication of time; I've seen this in many scripts too.

2)

Quoted Text INT. ROOM - DAY Jerdol lights a cigarette. INT. ROOM - LATER Jerdol puts out the cigarette.

As much as I believe that michel's advice was given with good intentions, don't use scene transitions and camera directions in spec scripts. That's the director's territory and by including them, your script screams 'amateur'.

If you're just starting the scene without any transitional scene prior to it, you could just write it as:

INT.  DAVID'S OFFICE

If the there was a prior scene of him leaving for his office (and announcing it) you could write:

INT.  DAVID'S OFFICE -LATER.



In regards to showing passing time, you have to write in a visual that tells the readers that:

A pile of cigarette butts in an ashtray that was clean earlier;
A clock on the wall changing time;
The cleaning crew coming in to empty the garbage.
Etc.


Phil

2) It is also acceptable to use a secondary heading within a scene to indicate the passing of time.

EXT. PARK - DAY

Bob paces under a tree.

LATER

Bob sleeps under the tree.

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1) Space films are notorious for having a lack of time (day or night) so a lot of the slugs exist without the time part since there is no time to give. If you are underground and don't wish to indicate the time, don't include it. I feel that since it would be impossible for the audience to tell the time on screen, there is no reason to include it in the script.

Thinking about this a bit more, you could keep it a little mysterious to begin with and open with INT. ROOM. That'll keep 'em guessing.