This is a chance once in a blue moon.

　　这是个千载难逢的机会。

　　blue moon 在现代天文学意义上指：“一个月中的第二次满月”，由于月运周期是29.5天，而根据日历，每个月大多数都有至少30天，因此，大约每32个月才会出现一次一个月两次圆月的现象。所以这个习语用以形容这种罕见的天文现象，后来引申为：“极为罕见的事情，千载难逢的机会”。因此，当美国人说"This is a chance once in a blue moon."时，他/她要表达的意思就是:"It is a golden opportunity."、"It is an once-in-a-lifetime opportunity."。

　　情景对白：

　　Terry: Frankly speaking, the boss always thinks highly of you. Why do you want to leave?

　　泰瑞：坦白地说，老板一直都很器重你。你为什么要走呢？

　　Benjamin: A friend of mine introduced me to his company which I have been dreaming to enter. This is a chance once in a blue moon.

　　本杰明：一个朋友介绍我去他们公司，那可是我做梦都想去的公司啊。这是个千载难逢的机会。

　　搭配句积累：

　　①I've got an offer of that company which is number one in this industry.

　　我收到了那家公司的录用函，它在行业内可是排名第一的哦。

　　②That company seldom holds outside recruit for senior managers.

　　那家公司很少从外部招聘资深经理。

　　③My boss allows me to resign before time.

　　老板允许我提前辞职了。

　　④My research has gained support from the government. So I'd like to quit.

　　我的研究已取得政府支持，所以我想辞职。

　　单词：

　　1. once-in-a-lifetime 千载难逢的

　　You can't pass up this job. This kind of opportunity comes only once in a lifetime.

　　你不可错过这个工作。这种机会一辈子才有一次。

　　It's definitely a once-in-a-lifetime experience.

　　这绝对是一次毕生难忘的体验。

　　2. before time 提前

　　Against all the odds, I finished my work well before time that I wanted to leave.

　　尽管非常困难，在我打算要离开之前，我早早完成了工作.

　　eg. She went there before time , taking the papers with her.

　　她带着文件提早到那里去。