js计算两个时间相差的天数

day1='2014-03-31 00:00:01';

function get_day(day1,day2){
var s = day1;
var dt = Date.parse(s.replace(/-/g,"/"));
var day1 = new Date(dt);

var s = day2;
var dt = Date.parse(s.replace(/-/g,"/"));
var day2 = new Date(dt);

var date3=day1.getTime()-day2.getTime()  //时间差的毫秒数
//计算出相差天数
return Math.floor(date3/(24*3600*1000))
}