PHP获取自然周列表，周开始结束日期，月开始结束时间方法类

自己写的几个获取 一年的自然周列表，一周的开始结束时间，一个月的开始结束时间的方法函数。请多大家多多批评指正！！！

<?php

function GetWeekList($year,$weekcurrent)
{
    if ($year%4==0 && ($year%100!=0 || $year%400==0))
    {
        $days=366;    
    }
    else
    {
        $days=365;
    }
    $weeks=substr($days/7,0,2);//计算一年有多少个星期

    $weeklist=array();
    $wc=1;
    for($w=0;$w<$weekcurrent-1;$w++)
    {
        $WeekDate=GetWeekDate($year,$wc,'3');
        $startime=date("Y-m-d",$WeekDate[0]);
        $endtime=date("Y-m-d",$WeekDate[1]);

        $weeklist[$w]["id"]=$wc;
        $weeklist[$w]["name"]=$year." 年, 第 ".$wc." 周 ($startime - $endtime)";
        $wc++;
    }

    return $weeklist;
}

/////////////////////////////////计算一周的开始结束时间//////////////////////////////////////////
function GetWeekDate($year,$week,$startcount)
{
    $timestamp = mktime(0,0,0,1,1,$year);
    $dayofweek = date("w",$timestamp);
    $distance = ($week-1)*7-$dayofweek+1+$startcount;
    $passed_seconds = $distance * 86400;
    $timestamp += $passed_seconds;  
    $first_date_of_week = $timestamp; //date("Ymd",$timestamp);
    $distance = 7;
    $timestamp += $distance * 86400;
    $last_date_of_week = $timestamp; //date("Ymd",$timestamp);

    $startime=$first_date_of_week;
    $endtime=$last_date_of_week;

    $WeekDate=array($startime,$endtime);

    return $WeekDate;
}

function GetMonthList($year,$monthcurrent)
{
    $mc=1;
    for($m=0;$m<12;$m++)
    {
        $monthlist[$m]["id"]=$mc;
        $monthlist[$m]["name"]=$year." 年，".$mc." 月 ";
        $mc++;
    }

    return $monthlist;
}

///////////////////////////////计算一个月的开始结束时间//////////////////////////////////////////
function GetMonthDate($year,$month)
{
    if($month<10)
    {
        $month="0".$month;
    }
    $startime=$year."-".$month."-01";

    //$months1=array(1,3,5,7,8,10,12);
    $months=array(4,6,9,11);

    if($month=="2")
    {
        if ($year%4==0 && ($year%100!=0 || $year%400==0))
        {
            $endtime=$year."-".$month."-29 24:00:00";
        }
        else
        {
            $endtime=$year."-".$month."-28 24:00:00";
        }
    }
    else if(in_array($month,$months))
    {
        $endtime=$year."-".$month."-30 24:00:00";
    }
    else
    {        
        $endtime=$year."-".$month."-31 24:00:00";
    }

    $MonthDate=array($startime,$endtime);

    return $MonthDate;

}

?>