I don't know how long records have been kept, but even if we can go back 500 yrs is that enough time given how old the earth is to say with any certainty?

我不知道目前有多长的记录。但是连地球的年龄至今都没有确切的结论，即便我们可以追溯到500年前的地震记录，它们是不是足以说明问题呢？

youdao

One person may go from Phase 4 to Phase 5 and then back to Phase 2 again; that is why there is no easy way to determine how long a change will take to implement.

有些人可能已从第四阶段进入第五阶段，但一下子又从新跳入第二阶段；这就是为什么计算一场变革需要花多长时间是很难的。

youdao

No matter how long have we been outside, we all want to go back home and back to the initial ourselves.

无论出发多久，都希望能够到回家、回归最初的自我。

youdao

One mother said it was "not fair that only well off people are able to choose how long they can spend off work while poorer people have to go back to work".

BBC: UK bosses urge MEPs to vote against EU maternity plans