The novel is an expansion of a short story he wrote about forty years ago.

这部小说是由一篇大约四十年前他写的短篇小说扩展而成。

youdao

It's underwater for three hundred years until they dug it up about forty years ago.

在水下沉了300年，直到40年前被挖掘出来。

youdao

I went through my midlife crisis about four or five years ago, when I was forty.

在我40岁时，我经历了中年危机。

《柯林斯英汉双解大词典》

The Aurignacian culture began about forty thousand years ago and ended about twenty-eight thousand years ago.

VOA: special.2009.08.18

The new Ang Lee film is not about the great historical happening of forty years ago but about Elliot Teichberg (Demetri Martin), whose parents run a Borscht Belt motel.

NEWYORKER: Taking Woodstock

But he could just as easily have been talking about the Xerox of forty years ago, which was one of the most successful makers of enterprise technology the world has ever known.

NEWYORKER: Creation Myth