Date.prototype.getUTCDay()
The getUTCDay() method returns the day of the week in the
specified date according to universal time, where 0 represents Sunday.
Syntax
getUTCDay()
Return value
A number.
If the Date object represents a valid date, an integer number corresponding to the day
of the week for the given date, according to universal time: 0 for Sunday, 1 for Monday,
2 for Tuesday, and so on.
Otherwise, NaN
if the Date object doesn't represent a valid date.