三人行，必有我师(焉)

语法
Question word + 都, "every~" (谁都 = everyone, 哪儿都 = everywhere, 什么时候都 = all the time, 多少都 = however much, 怎么都 = however)
https://resources.allsetlearning.com/chinese/grammar/Expressing_%22every%22_with_question_words

词汇
当 when (among other meanings), 当时, at that time ( pinyin )
(I've also seen 当年 used a lot to mean "back then" rather than "in that year" specifically, I think)
https://mandarinbean.com/new-hsk-2-word-list/

Guardian:
这句话谁都可以说，但是你不可以, everyone can say this, but you can't
我的家不在这里，哪里都不在, my home isn't here, it isn't anywhere
当时我以为你是个怪物，就下意识地动了手, at that point I thought you were a monster, so my hand moved unconsciously

Me:
那家餐厅非常方便，什么时候来都可以吃饭。
当时我一点也没说中文。