若不强调时间的期间，而强调时间的起点，morning, afternoon, evening前面通常不用冠词。如：
Afternoon came, and it was time for them to leave. 下午到了，是他们起程的时候了。
It happened towards evening the next day. 这事发生在次日傍晚。
When morning came, I found that she had left. 天亮了，我发现她已走了。
比较：Night began to fall. 夜幕开始降临。