Time

Time
 

-These things can be closely related to the background of the time Cynthia lived __.

Could I use in? It sounds OK to me, but my friend says in is wrong and only at is possible. Who is correct?

Both 'in' and 'at' can be used.
Your sentence works well with 'in'.

You can live in a time and you can live at a time. The distinction, in my mind anyway, is that 'in' is more general (within or inside a broad definition of time, like an age or an era) and that 'at' focuses on a more specific instance of time, like a date, an event or a memory).

Thanks.

If age/era=a particular period of history, could we use both at and in?

-We are living at the internet age.
-We are living in the internet age.
-We are living at the internet era.
-We are living in the internet era.

in the internet age
in the internet era

Excellent answer. Thank you.