获取当前的时间戳n2和一年开始的时间戳n1，然后相减，计算出已过去的天数pday，

最后pday除以今年的总天数tday算出百分比percent

function yearPastPercent(){
	var year=new Date().getFullYear()
	var tday=( year%4==0 && year%100!=0 || year%400==0 )? 366 : 365
	var n1 = Date.parse(new Date(year,1-1,1))
	var n2 = Date.parse(new Date())
	var pday = (n2-n1)/(1000 * 60 * 60 * 24)
	var percent = Math.ceil(pday/tday*10000)/100
	return percent
}
document.write('程园丁提示：今年已过去了 '+yearPastPercent()+'%')