使用PHP实现计算两个日期间隔的年、月、周、日数:

strtotime($b)) list($a,$b)=array($b,$a);        $start  = strtotime($a);        $stop   = strtotime($b);        $extend = ($stop-$start)/86400;        $result['extends'] = $extend;        if($extend<7){                //如果小于7天直接返回天数            $result['daily'] = $extend;        }elseif($extend<=31){        //小于28天则返回周数，由于闰年2月满足了            if($stop==strtotime($a.'+1 month')){                $result['monthly'] = 1;            }else{                $w = floor($extend/7);                $d = ($stop-strtotime($a.'+'.$w.' week'))/86400;                $result['weekly']  = $w;                $result['daily']   = $d;            }        }else{            $y=    floor($extend/365);            if($y>=1){                //如果超过一年                $start = strtotime($a.'+'.$y.'year');                $a     = date('Y-m-d',$start);                //判断是否真的已经有了一年了，如果没有的话就开减                if($start>$stop){                    $a = date('Y-m-d',strtotime($a.'-1 month'));                    $m =11;                    $y--;                    }                $extend = ($stop-strtotime($a))/86400;            }            if(isset($m)){                $w = floor($extend/7);                $d = $extend-$w*7;            }else{                $m = isset($m)?$m:round($extend/30);                $stop>=strtotime($a.'+'.$m.'month')?$m:$m--;                if($stop>=strtotime($a.'+'.$m.'month')){                    $d=$w=($stop-strtotime($a.'+'.$m.'month'))/86400;                    $w = floor($w/7);                    $d = $d-$w*7;                }            }            $result['yearly']  = $y;            $result['monthly'] = $m;            $result['weekly']  = $w;            $result['daily']   = isset($d)?$d:null;        }        return array_filter($result);    }    print_r(format('2012-10-1','2012-12-15'));?>

运行结果：
Array([extends]=>75[monthly]=>2[weekly]=>2)

php 查询某天所在的周数及对应周的起始日期

/**
* @file
* @version  1.1
* @author  QQ83989686
* @date  2012-8-7 最后修改时间
* @brief
*/
    //获取某个日期的 周数、周对应的开始结束时间
    private function getWeekStartEndDay($day)
    {
        $g  = strftime("%u",strtotime($day));
        return array('week_num'=>strftime("%V",strtotime($day)),'week_start_day'=>strftime('%Y-%m-%d',strtotime($day)-($g-1)*86400),'week_start_day_cn'=>strftime('%Y年%m月%d日',strtotime($day)-($g-1)*86400),'week_end_day'=>strftime('%Y-%m-%d',strtotime($day) + (7-$g)*86400),'week_end_day_cn'=>strftime('%Y年%m月%d日',strtotime($day) + (7-$g)*86400));
    }