Given that you haven't provided any criteria for how to determine what quarter *we are currently in, an algorithm can be suggested that you must then adapt to whatever criteria you need. e.g.

// For the US Government fiscal year

// Oct-Dec = 1

// Jan-Mar = 2

// Apr-Jun = 3

// Jul-Sep = 4

function getQuarter(d) {

  d = d || new Date();

  var m = Math.floor(d.getMonth()/3) + 2;

  return m > 4? m - 4 : m;

}

As a runnable snippet and including the year:

function getQuarter(d) {

  d = d || new Date();

  var m = Math.floor(d.getMonth() / 3) + 2;

  m -= m > 4 ? 4 : 0;

  var y = d.getFullYear() + (m == 1? 1 : 0);

  return [y,m];

}



console.log(`The current US fiscal quarter is ${getQuarter().join('Q')}`);

console.log(`1 July 2018 is ${getQuarter(new Date(2018,6,1)).join('Q')}`);

You can then adapt that to the various financial or calendar quarters as appropriate. You can also do:

function getQuarter(d) {

  d = d || new Date(); // If no date supplied, use today

  var q = [4,1,2,3];

  return q[Math.floor(d.getMonth() / 3)];

}

Then use different q arrays depending on the definition of quarter required.

Edit

The following gets the days remaining in a quarter if they start on 1 Jan, Apr, Jul and Oct, It's tested in various browsers, including IE 6 (though since it uses basic ECMAScript it should work everywhere):

function daysLeftInQuarter(d) {

  d = d || new Date();

  var qEnd = new Date(d);

  qEnd.setMonth(qEnd.getMonth() + 3 - qEnd.getMonth() % 3, 0);

  return Math.floor((qEnd - d) / 8.64e7);

}