idiom · to lose consciousness or experience a loss of vision due to dizziness

他只觉得头重脚轻，眼前一阵昏天黑地，晕倒了过去。

idiom · a state of great disorder, social upheaval, or troubled times

那个时代的政局动荡，闹得昏天黑地。

idiom · pitch black or extremely dark, describing the physical environment or weather

沙尘暴突然袭来，一时间昏天黑地。