It specifies the day which will be holiday as string array through days property.
The day string follows the week abbreviation which has been set in grid Locale. Holiday type value is "day" in column editor setting.
var columns = [{
editor: {
type: "date",
holidays: [{
type: "day",
days: ["Sat.", "Sun."]
}]
}
},
...
];
grid.setColumns(columns);