Definition
a specific period or era in history.
时期；时代
How did people communicate in the days before email?
在电子邮件出现之前，人们是如何沟通的？
Those were the days before antibiotics, when illnesses like that could be fatal.
那是抗生素出现前的时代，那样的疾病可能是致命的。
This is how people managed in the days before air conditioning was invented.
这就是人们在空调发明之前是如何应对的。