If the date falls on a Wednesday, the holiday is the preceding Monday. If it falls on a Thursday then the holiday is the following Monday.
If the holiday is on Tuesday, Monday is added as a holiday day. if the holiday is on Thursday, then Friday is granted as holiday.
The rules above can lead to a lot of annual Public holidays, but most Argentinians only get 10 vacation days, rising to 15 days if they have worked for more than 5 years in a company.