Why does my addDays method work for some parameters but not others?

I am working on an APCS assignment to make a date class, and in it we needed an addDays method that add days to a date. So for example in the client code it would say date1.addDays(60000)

My code works for some addDays (ex. 1000) but doesn't work for others (ex. 60000)

public void addDays(int days){
    while(days>0){            
            day++;
            days--;
            if(day>daysInMonth(month)){
                month++;
                day = 1;
            }
            if(month>12){
                year++;
                month = 1;
                day = 1;
            }
    }
}