code: function getDate(ymValue) {
  	checkNumber(ymValue)
  	var utcFullYear = Math.floor(ymValue / monthsPerYear) + zeroUtcFullYear
  	var utcMonth = modFix(Math.floor(ymValue), monthsPerYear) + zeroUtcMonth
  	return new Date(Date.UTC(utcFullYear, utcMonth))
  }
docs: convert linearValue to Date object