While I was reading class material from a language school in Korea, I found a whole unit explaining use of the past perfect.
However, none of the sentences used a time clause with the simple past to go with the main clause with the past perfect.
All of the sentences just used the phrase "the day before".
I had eaten the day before.
Is it correct to use the past perfect without a time clause with the simple past ?
Ok, I found some other conversations.
A: Did you have chicken for dinner yesterday ?
B: No, I didn't. I had had chicken for dinner the day before.
Is this okay because there is a reference time ?