new Date from year month js code example

Example 1: javascript get day of year from date

//Month -> 0= Jan, 11=Dec | myDate = 6 Dec 2019 10:45
var myDate = new Date(2019, 11, 06, 10, 45);
var dayInYear = Math.floor((myDate - new Date(myDate.getFullYear(), 0, 0)) / (1000 * 60 * 60 * 24));

Example 2: new date() javascript

var date = new Date(); //Will use computers date by default.
//parameters will specify date you put to input
var date = new Date(year, month, day, hours, minutes, seconds, milliseconds);