In MCF (Make Continents Fast) the room long description section would contain:

    #DYou are in Someone's office where
    [(({time.hour}>5)&&({time.hour}<20))] sunlight |
    [{time.hour}<6] moonlight |
    [{time.hour}>19] moonlight |
    streams through a skylight.

If the time was between 6 o'clock and 19 o'clock the result of looking at
the room would be:

Someone's Office
[Exits: north ]
You are in Someone's office where sunlight streams through a skylight.

If the time was before 6 o'clock or after 19 o'clock it would be:

Someone's Office
[Exits: north ]
You are in Someone's office where moonlight streams through a skylight.

but let's also do this a more simple way to see how that syntax looks:

    #DYou are in Someone's office where
    [{time.day}] sunlight |
    [{time.morning}] moonlight |
    [{time.evening}] moonlight |
    streams through a skylight.

or even:

    #DYou are in Someone's office where
    [{time.day}] sunlight |
    [{time.day} == {false}] moonlight |
    streams through a skylight.

Note that "== {false}" must be added to the second calculation to make
the result of the calculation "true" when it is not day and cause
"moonlight" to be displayed at night.