I'd like to find out the times in the history of a question when it was closed and reopened. How can I do that using API v2?

The closest relevant call I have found is /questions/{ids}/timeline, which returns a list of question_timeline, which has a timeline_type field that could be post_state_changed. However, there doesn't seem to be any way to find out what that state changed to: was is closed? reopened? locked? unlocked? wikified?

It seems to me that the question_timeline data are incomplete, and the API should be enhanced. (Or, if there is a way to extract that information, then it should be clarified in the documentation.)

I've also looked at /questions/{ids}, which tells you the closed_date. Since there is no reopened_date, I conclude that closed_date would only be present if the question is currently closed, and that it doesn't tell you anything about historical state transitions.