noun
nightfall
NYTE-fawl/ˈnaɪtfɔːl/
The time when darkness begins in the evening.
At nightfall, the village windows glow beneath the first stars.

Etymology
Night combines with fall in its sense of “coming on”: darkness is pictured as falling. The compound names the transition into night, rather than the whole dark period.
In context
They can never finish them off completely before nightfall. And actually all night the Spanish kind of hunker down slightly