Learn English – the difference between “at the time” and “in the time” when they refer to a period of time

prepositional-phrasesprepositionstime

From the page about Oscar Wilde on OALD:

E1. In 1895 he was sent to prison for his homosexuality, which was illegal at the time.

And here is a chunk from my post on Lang-8. No one has changed in to at so far.

E2. This year, I received a Bachelor's degree in biology, and now I am studying for a Master's degree. I am doing the same research I did in that time.

What I have found on the topic:

In that time suggests during a period of time: e.g. in that time I managed to undo the knot.

At that time suggests at a particular moment, or period: e.g. at that time I was fond of talking Esperanto.
Source: at that time / in that time — WordReference Forums

To be honest, after that explanation I don't see any difference between at and in in the examples I wrote above, since both are referring to a period.

Do these uses differ from each other when referring to a period, and what is this difference?

After a little thinking: should I have written the exact years of my study to use at in E2?

Best Answer

I would certainly change your sentence to "at that time".

What I believe you are missing is that "in" implies a duration and the phrase is actually a shortened version of "within" and skipping "amount of":

[with]in that [amount of] time I managed to undo the knot.

This means:

  • I was given some amount of time
  • I was able to complete the task

A longer version of the sentence, to put it in context, would be something like:

I was tied up in a closet and knew the bomb would go off in two minutes. In that time I managed to undo the knot, get out of the closet and escape the building just before it exploded.

And, if you were telling the story to someone, you might include "at that time":

A: Where were you yesterday evening?
B: I was tied up in a closet at that time and a bomb was going to go off in two minutes.

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