How to set schedule for a particular date

I have my Scheduler set for Mon - Fri 12:00 pm - 4:00 p.m.  If I have appointments on a Monday for example, can I change my availability for that date only or do I have to uncheck Monday and have to remember to go back in and activate it for the following Monday?  I’m looking for a way to say I’m not available for that particular Monday and not have to uncheck Monday making me unavailable for ALL Mondays unless I remember to re-check that day.  TIA