I hope this is not a double post.
Should I use "at the time" or "at that time" when I want to express something that was known during the time when the events occurred?
Bonco presents the facts known at the time about Fiolo and their interpretation by various authors.
Here I mean "at the time" as "at the moment that Bonco wrote it."
Best Answer
Both should be equally acceptable in most contexts. In rare cases, "at that time" might cause some slight confusion if it makes it appear as though you are setting up a comparison with some other, different time ("This time? No, that time!"). Mostly, though, it's a matter of sentence flow and which one you like the best.