java 获取当天（今日）零点零分零秒

日期格式

Calendar calendar = Calendar.getInstance();
calendar.setTime(new Date());
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
Date zero = calendar.getTime();;

时间戳格式

long current = System.currentTimeMillis();
long zero = current - (current + TimeZone.getDefault().getRawOffset() )% (1000*3600*24)