静态成员函数为什么不能调用静态数组呢？？？？

#include <iostream>
using namespace std;
class Event{
    private:
        int day;
        int month;
        static int year;
        static int m[13];
    public:
        int getDay(){return day;}
        int getMonth(){return month;}
        void setDay(int d){day = d;}
        void setMonth(int m){month = m;}
        void setYear(int y){ year = y;}
        int getYear(){return year;}
        int operator-(Event & e);
        static void setM();
};

int Event::year = 2012;  //静态变量类外初始化
int Event::m[13] = {0};  //静态变量类外初始化
void Event::setM(){
            int i,j;
            for(i = 1,j = 12;i < j;i++,j--){
                if(i%2)
                     m[i] = m[j] =31;
                 else
                     m[i] = m[j] =30;
                }
                m[7] = 31;
                if(year % 4)
                    m[2] = 29;
                else
                    m[2] = 28;
}
int Event::operator-(Event & e)
{
    Event::setM();
    return 1;    //这个地方要么返回一个值，要么不返回，你看着修改
}

int main()
{
    return 0;
}