In this task, you're given an open-domain question. Your task is to provide an answer to the given question. There is only one unique answer for each question. Your answer should be short, and refer to an entity, date, number, etc. Do not put your answer in the context of a sentence.

When did leningrad changed back to st petersburg?
6 September 1991

What does the rosenberg self esteem scale measure?
self-esteem

When was the term dark ages first used?

1330s