function getProcent() {

    var dateToPrint = {
      1: 'A',
      2: 'Б',
      3: 'В',
    }

    var dayStart = new Date(2017, 03, 24);
    var dayCurrent = Date.now();

    var dayDiff = ((dayCurrent - dayStart) / 86400000);

    if (dayDiff <= 21) {

      var ceil = Math.ceil(dayDiff / 7);
    } else {

      var floor = Math.floor(dayDiff / 21);

      var leftEnd = floor * 21;
      var newStart = dayDiff - leftEnd;

      var ceil = Math.ceil(newStart / 7);
    }

    var data = dateToPrint[ceil];
    var div = document.getElementsByClassName('dateToPrint');

    for (var i = 0; i < div.length; i++) {
      div.item(i).innerHTML = data;
    }
  }