You can schedule it for a particular date every month (i.e. 15th of every month).
The screenshot above illustrates how you can schedule a report to run on the 4th of every month. If you schedule a report for 29/30/31 of any month, it will automatically run on the last day of the month which does not have 29/30/31 days. Hope this makes sense. Scheduling it for 4th Friday etc is not possible today. Adding that paradigm to our current report scheduling feature is not something we are planning in the near future.