Is it more correct to say at the same time or in the same time? Thanks in advance!

Question

Answer

They both work and have different usages. "At" marks a specific time, "in" indicates within a duration of time.

We came home at the same time.
I ran 100m in the same time it took you to run 200m.

Answer

You MUST say /in the same time/ when you express that two or more things
took an equal length of time to be done, that is, when the time is not a precise moment, but is a duration.

They run the marathon in the same time, although their age was quite different;
the judges had an hard time we deciding who the winner was.

Answer

Generally: at the same time.

Answer

Do also others see a face in the waterfall, or is it just my illusion ?

Answer

I agree with Jon, but if you mean "simultaneously" then the phrase is "at the same time".