The interval may be assumed to have been a major formative period in his life: he was 21 years old when it began, 31 when it concluded.

但是这段时间可以被认为是一个人的成形时间(formative period)：开始于他21岁，终止于他31岁那年。

youdao

The interval may be assumed to have been a major formative period in his life: he was 21 years old when it began, 31 when it concluded.

但是这段时间可以被认为是一个人的成形时间(formative period)：开始于他21岁，终止于他31岁那年。

youdao