SimpleDateFormat sf = new SimpleDateFormat( "yyyy-MM-dd");
Date d = sf.parse(date);
long dl = d.getTime();
int num = 30;//
long dayM = 24*60*60*1000;
long l = during*num*dayM ;
计算date+2个月-15天
long res = dl+l-15*dayM;
Date temp = new Date(res);
结果sf.format(temp);