java时间格式

Calendar startdate = Calendar.getInstance();
startdate.setTime(new Date()); //当前时间
startdate.add(Calendar.YEAR,-2); //将当前时间的年份减2
startdate.set(Calendar.MONTH,0);
//将小时至0
startdate.set(Calendar.HOUR_OF_DAY, 0);
//将分钟至0
startdate.set(Calendar.MINUTE, 0);
//将秒至0
startdate.set(Calendar.SECOND,0);
//将毫秒至0
startdate.set(Calendar.MILLISECOND, 0);
startdate.set(Calendar.DATE,1); //将日期置为1