Im trying to change the fullcalendar (v3) day cell background-color for specific days declared in a databse table. So far i was able to try it with manual input for only one day which works fine with the following code:

        dayRender: function (date, cell) {
            
            var day_declared_in_database = '2022-05-13';
            
            var specific_day = moment('' + day_declared_in_database + 'T00:00Z');
            if (date.isSame(specific_day, "day")) {
                cell.css("background-color", "blue");
            }
        },

Any idea how to get external data into dayRender and loop through all days to apply the color to multiple different days?