Ira,
This can be done by creating a Workflow with a Schedule Condition Setting up the Interval - Specific Day(s) of the month - 15 Close and save the Workflow.
Then you would have to go to the Repository tab - to the condition that you just created - right mouse click then select exclusion - Got to Properties then Condition Exclusions. You can add holidays here and this will exclude the holidays by country.
Thanks, Chris