How to monitor history of database usage if login auditing is not enabled?
I blogged about it exactly one month ago. Since link-only answers are discouraged and pasting here the whole blog post would be ridiculous, here is a summary of what you will find there.

Basically, you have to record index usage in a user table, in order to make sure that server restarts and index maintenance don't delete entries for the databases you're interested in.

A second method involves auditing index usage by means of streaming an Extended Events session that captures lock acquired events. This method is particularly useful for capturing additional information about who is accessing the tables without having to capture detail information (audits and XE file targets would be too verbose for this task). 

I hope you find it useful.