good day

英 [ˌɡʊd ˈdeɪ]

美 [ˌɡʊd ˈdeɪ]

int. (白天见面或分手时用语)白天好，你(们)好，再见

牛津词典

exclamation

（白天见面或分手时用语）白天好，你（们）好，再见
used to say hello or goodbye politely when people first see each other or leave each other during the day
1. Good day to you.
  你好。

CONVENTION （问候用语，代替Hello及Goodbye）你（们）好，再见
People sometimes say 'Good day' instead of 'Hello' or 'Goodbye'.
1. Well, I'd better be off. Good day to you.
  好啦，我得走了，再见。

noun

It is a good day to catch up on back reading and other assignments.
周日用来补上拖欠的阅读任务和其他作业的好时机。
I'm sorry to complain so much. It's just not a good day.
我很抱歉发了这么多牢骚。今天可不是个好日子。
It's a good day for playing practical jokes on your friends.
这是一个对你的朋友们开实际玩笑的好日子。
Too good today, that is a good day yesterday!
过好了今天，也就是明天有了好的昨天！
Wednesday would be a good day for us to go running.
星期三将是我们去跑步的一个好日子。
It's a good day for an important meeting because things are sure to go your way.
这也是个举行重要会议的好日子，因为事情开始顺应你的期待而动了。
Have a good day.
有一个早晨好。
Today is a good day, the rain stopped;
今天是个好日子，大雨停了；
The three friends have a good day.
这三个朋友度过了愉快的一天。
I hope that all of you have a good day.
我希望你们都有美好的一天。