A function to calculate the difference between days

calcDaysDiff.js

function calcDaysDiff( start, end ) {
  var currentDate = start || new Date(),
      timeDiff = end - currentDate,
      timeUnit = 24 * 60 * 60 * 1000,
      diff = 0;
      
  diff = (timeDiff - currentDate % timeUnit) / timeUnit + 1;
  return Math.floor(diff);
}

oh ty