at that time
prep. phr..prep. phr.. This phrase refers to a specific moment in the past that you have already mentioned.
prep. phr.. A temporal adverbial phrase that anchors an event to a previously established point in the past.
At that time, I was a student in college.
I first visited Paris in 1999; at that time, the city felt completely different.
The company was pioneering new technology, and at that time, its founders could scarcely imagine the global impact their work would have.
It refers to a specific past moment that has already been mentioned in the conversation or text.
Contrast with 'at this time' (referring to the present) and 'at the time' (a more general reference to a past period).
In that time, we didn't have smartphones.At that time, we didn't have smartphones.The correct preposition for referring to a specific point in time is 'at', not 'in'.