When to use "where" and "that"?
She had never stopped crying for her parents in all those years that he kept her prisoner.
2016 was the year (that) I was born.
The first sentence is from a book and the second is from the internet. I'm confused by the the usage of "that" in sentences like this. Is "that" optional? Can it be dropped?
Also in what cases do we use "where" as a relative?
And how about "when"?
Thanks in advance!

