Попробуйте это:
html компонента
Selected Date is: <b>{{getDay(model)}}</b>
ts компонента
getDay(model){
let date = new Date(Date.UTC(model.year, model.month - 1, model.day, 0, 0, 0))
let days = new Array( "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" );
let day = days[date.getDay() - 1]
return day
}