释义：

have a good day ( time ) 祝你过得愉快

一天不如意时可以说 I had a bad day，一天很开心时可以说 I am having a good time。当然，也可以像 have a nice trip一样，接除了 day ( time ) 以外的其他名词。

例句：

I've got to get some sleep. I had a rough day.
我得去睡觉了。今天过得很累。
I'm having a hard time these days.
我最近过得不好。
I'm just here with my friends having a good time.
我和朋友们在一起玩得很嗨。
Did you guys have a good time in Japan?
你们在日本玩得怎么样？

对话：

A: I'll be traveling in Europe for three weeks.
我要去欧洲旅行三个星期。
B: Have a good time. I really envy you.
祝你玩得愉快，说实话，羡慕死你了。