get sprint dates

sprints.js

(function() {
  const startDay = new Date('01/04/2021');
  let currentDay = new Date(startDay.getTime());
  let sprintNo = 1;

  while (currentDay.getYear() == startDay.getYear()) {
    let endDay = new Date(currentDay.getTime());
    endDay.setDate(endDay.getDate() + 11);
    console.log(fSprint(sprintNo++), fDate(currentDay), fDate(endDay));
    currentDay.setDate(currentDay.getDate() + 14);
  }

  function fSprint(sprint) {
    const sprintNo = (sprint + 100).toString().substring(1);
    return `2021-${sprintNo}`;
  }

  function fDate(date) {
    const day = (date.getDate() + 100).toString().substring(1);
    const month = (date.getMonth() + 101).toString().substring(1);
    const year = date.getFullYear().toString();
    return `${year}-${month}-${day}`;
  }
})();