code: function isValidDate(year, month, date) { // eslint-disable-line complexity
      var isValidYear, isValidMonth, isValid, lastDayInMonth;
  
      year = Number(year);
      month = Number(month);
      date = Number(date);
  
      isValidYear = (year > -1 && year < 100) || ((year > 1969) && (year < 2070));
      isValidMonth = (month > 0) && (month < 13);
  
      if (!isValidYear || !isValidMonth) {
          return false;
      }
  
      lastDayInMonth = MONTH_DAYS[month];
      if (month === 2 && year % 4 === 0) {
          if (year % 100 !== 0 || year % 400 === 0) {
              lastDayInMonth = 29;
          }
      }
  
      isValid = (date > 0) && (date <= lastDayInMonth);
  
      return isValid;
  }
docs: Check whether the given variables are valid date or not.
  @param {number} year - Year
  @param {number} month - Month
  @param {number} date - Day in month.
  @returns {boolean} Is valid?
  @private