javaScript的日期函数

<script>
//当天
     function showToDay()
    {
        var Nowdate=new Date();
        M=Number(Nowdate.getMonth())+1
        return Nowdate.getYear()+"-"+M+"-"+Nowdate.getDate();
    }   

   
    //本周第一天
     function showWeekFirstDay()


    {
        var Nowdate=new Date();
        var WeekFirstDay=new Date(Nowdate-(Nowdate.getDay()-1)*86400000);
        return WeekFirstDay;
    }
    //本周最后一天
     function showWeekLastDay()
    {
        var Nowdate=new Date();
        var WeekFirstDay=new Date(Nowdate-(Nowdate.getDay()-1)*86400000);
        var WeekLastDay=new Date((WeekFirstDay/1000+6*86400)*1000);
        return WeekLastDay;
    }
    //本月第一天
     function showMonthFirstDay()
    {
        var Nowdate=new Date();
        var MonthFirstDay=new Date(Nowdate.getYear(),Nowdate.getMonth(),1);
        return MonthFirstDay;
    }

    //本月最后一天


     function showMonthLastDay()
    {
        var Nowdate=new Date();
        var tmpDate=new Date(Nowdate.getYear(),Nowdate.getMonth()+1,1);
        //tmpDate.setDate(tmpDate.getDate() -1);
        //return new Date(Nowdate.getYear(),Nowdate.getMonth(),tmpDate.getDate());
        var MonthLastDay=new Date(tmpDate-86400000);
        return MonthLastDay;


    }


   
    //本季第一天
     function showquarterFirstDay()
    {
        var Nowdate=new Date();
        if(Nowdate.getMonth()<3)
           return new Date(Nowdate.getYear(),0,1);
        else if(Nowdate.getMonth()>2 && Nowdate.getMonth()<6)
           return new Date(Nowdate.getYear(),3,1);
        else if(Nowdate.getMonth()>5 && Nowdate.getMonth()<9)
           return new Date(Nowdate.getYear(),6,1);
        else if(Nowdate.getMonth()>8)
           return new Date(Nowdate.getYear(),9,1);
    }

    //本季最后一天
     function showquarterLastDay()
    {
        var Nowdate=new Date();


        if(Nowdate.getMonth()<3)
           return new Date(Nowdate.getYear(),2,31);
        else if(Nowdate.getMonth()>2 && Nowdate.getMonth()<6)
           return new Date(Nowdate.getYear(),5,30);
        else if(Nowdate.getMonth()>5 && Nowdate.getMonth()<9)
           return new Date(Nowdate.getYear(),8,30);
        else if(Nowdate.getMonth()>8)
           return new Date(Nowdate.getYear(),11,31);
    }

   
    //本年第一天
     function showyearFirstDay()
    {
        var Nowdate=new Date();
        var yearFirstDay=new Date(Nowdate.getYear(),0,1);
        return yearFirstDay;
    }

    //本年最后一天
     function showyearLastDay()
    {
        var Nowdate=new Date();
        var yearLastDay=new Date(Nowdate.getYear(),11,31);
        return yearLastDay;
    }

   
    //当前月
     function showmonthCurrent()
    {
        var Nowdate=new Date();
        var Month=Nowdate.getMonth()+1;
        Month=(Month<10)?'-0'+Month:'-'+Month;
        return Nowdate.getYear()+Month;
    }
   
    //本季开始年月
     function showquarterFirstMonth()
    {
        var Nowdate=new Date();
        if(Nowdate.getMonth()<3)
            return Nowdate.getYear()+'-01';
        else if(Nowdate.getMonth()>2 && Nowdate.getMonth()<6)
            return Nowdate.getYear()+'-04';
        else if(Nowdate.getMonth()>5 && Nowdate.getMonth()<9)
            return Nowdate.getYear()+'-07';
        else if(Nowdate.getMonth()>8)
            return Nowdate.getYear()+'-10';
    }

    //本季最后年月
     function showquarterLastMonth()
    {
        var Nowdate=new Date();
        if(Nowdate.getMonth()<3)
            return Nowdate.getYear()+'-03';
        else if(Nowdate.getMonth()>2 && Nowdate.getMonth()<6)
            return Nowdate.getYear()+'-06';
        else if(Nowdate.getMonth()>5 && Nowdate.getMonth()<9)
            return Nowdate.getYear()+'-09';
        else if(Nowdate.getMonth()>8)
            return Nowdate.getYear()+'-12';
    }

   
    //本年开始年月
     function showyearFirstMonth()
    {
        var Nowdate=new Date();
        return Nowdate.getYear()+'-01';
    }

    //本年最后年月
     function showyearLastMonth()
    {
        var Nowdate=new Date();
        return Nowdate.getYear()+'-12';
    }
    //格式化日期格式
     function Date.prototype.toString(){
    return this.getFullYear()+"-"+(this.getMonth()+1)+"-"+this.getDate();
    }
    //判断瑞年
     boolean isLeap(int year)  
    {  
        if (((year % 100 == 0) && year % 400 == 0) || ((year % 100 != 0) && year % 4 == 0))  
            return true;  
        else 
            return false;  
    }  
//得到上个月的第一天和最后一天


     var d=new Date();
     var d1=new Date(d.getFullYear(),d.getMonth()-1,1);
     var d2=new Date(d.getFullYear(),d.getMonth(),0);
     alert(d1.toLocaleString()+" ; "+d2.toLocaleString())


</script>