白天=daytime，夜晚≠nighttime

可以看出，英语是一种不合逻辑的语言。

Daytime（白天）是一个词:night-time或night time（夜晚）则不是一个词。需要加连字符或者空格。

例句：

During the daytime he has to work and at night he must take care of their children.

他白天需要工作，晚上还要照顾孩子。

The government announced a night-time curfew.

政府宣布实行宵禁。

很多时候还可以不加“time”

例句：

During the day he has to work.

他白天需要工作。

These days everyone is working both day and night to finish the job on time.

这几天大家都在日以继夜地忙着完成任务。