Timestamp transDate = new Timestamp(System.currentTimeMillis());// 获取系统当前时间
// 构建日历对象,获取上月的当日
Calendar cal = Calendar.getInstance();
cal.setTime(transDate);
cal.add(Calendar.MONTH, -1);
// 将日历对象转变为Timestamp
transDate = new Timestamp(cal.getTimeInMillis());