Are the users registered in any way (e.g. have accounts)? You could check the login logs.
If not, you could also use something like UXWizz[0] to tag each individual session based on their user ID and then run a MySQL query to get the distinct ones within the last 30 days.
If not, you could also use something like UXWizz[0] to tag each individual session based on their user ID and then run a MySQL query to get the distinct ones within the last 30 days.
[0]: https://uxwizz.com