Chat queue availability report

Summary:

Historical report on how much time there was no agent available for a specific queue.

Content (required):

I'm looking for a historical report on how much time there was no agent available for a specific queue, perhaps broken down by date/time. I can see this data in the real-time reports (i.e. who is available and how many sessions are free). But I've been trying to either find an oob report or create one to tell me this information over the last 6 months. Just simply queue and date/times there were no available sessions. Any help is appreciated.