function isDateString(sDate)
{	var iaMonthDays = [31,28,31,30,31,30,31,31,30,31,30,31]
	var iaDate = new Array(3)
	var year, month, day

	if (arguments.length != 1) return false
	iaDate = sDate.toString().split("-")
	if (iaDate.length != 3) return false
	if (iaDate[1].length > 2 || iaDate[2].length > 2) return false
	if (isNaN(iaDate[0])||isNaN(iaDate[1])||isNaN(iaDate[2])) return false

	year = parseFloat(iaDate[0])
	month = parseFloat(iaDate[1])
	day=parseFloat(iaDate[2])

	if (year < 1900 || year > 2100) return false
	if (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) iaMonthDays[1]=29;
	if (month < 1 || month > 12) return false
	if (day < 1 || day > iaMonthDays[month - 1]) return false
	return true
}

function stringToDate(sDate, bIgnore)
{	var bValidDate, year, month, day
	var iaDate = new Array(3)
	
	if (bIgnore) bValidDate = true
	else bValidDate = isDateString(sDate)
	
	if (bValidDate)
	{  iaDate = sDate.toString().split("-")
		year = parseFloat(iaDate[0])
		month = parseFloat(iaDate[1]) - 1
		day=parseFloat(iaDate[2])
		return (new Date(year,month,day))
	}
	else return (new Date(1920,1,1))
}



/**
	功能：传进‘yyyy-mm-dd’日期，计算后返回加减天数（这里是7天）后的 ‘yyyy-mm-dd’ 日期。
**/  
function date2str(yy, mm, dd, prenext, addDays) {
    var s, d, t, t2;
    t = Date.UTC(yy, mm, dd);
    t2 = addDays * 1000 * 3600 * 24; //加减7天的时间
    if (prenext == 'pre') {
        t-= t2;
    } else {
        t+= t2;
    }
    d = new Date(t);

    s = d.getUTCFullYear() + "-";
    s += ("00"+(d.getUTCMonth()+1)).slice(-2) + "-";
    s += ("00"+d.getUTCDate()).slice(-2);

	
    return s;
}

function str2date(str, prenext, addDays){   
  var   dd, mm, yy;   
  var   reg = /^(\d{4})-(\d{1,2})-(\d{1,2})$/;
  if (arr = str.match(reg)) {
    yy = Number(arr[1]);
    mm = Number(arr[2])-1;
    dd = Number(arr[3]);
  } else {
    var d = new Date();
    yy = d.getUTCFullYear();
    mm = ("00"+(d.getUTCMonth())).slice(-2);
    dd = ("00"+d.getUTCDate()).slice(-2);
  }
 if (prenext == null || (prenext != 'pre' && prenext != 'next')) {
    var prenext = 'pre';
  }

  return date2str(yy, mm, dd, prenext, addDays);
}