计算前一个午夜的unix时间戳

Question

如何在Java中计算截断到午夜的unix时间戳？

PHP examples显示制作字符串然后再解析它们。肯定会有一种比Java更清晰的方式吗？

Answer 1

Unix时间戳从UTC午夜开始，因此我们可以执行以下操作

Calendar c = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
c.set(Calendar.HOUR_OF_DAY, 0);
c.set(Calendar.MINUTE, 0);
c.set(Calendar.SECOND, 0);
c.set(Calendar.MILLISECOND, 0);
long unixTimeStamp = c.getTimeInMillis() / 1000;

Answer 2

Calendar c = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
c.set(Calendar.HOUR,0);
c.set(Calendar.MINUTE,0);
c.set(Calendar.SECOND,0);
c.set(Calendar.MILLISECOND,0);

long midnightUnixTimestamp = c.getTime().getTime()/1000;

Answer 3

对于unix时间戳，您可以创建如下函数：

public long getMidnightTimestamp(long timestamp)
{
    return timestamp - timestamp % 86400; // 24 * 60 * 60 sec in one day 
}

并像这样使用它：

long currentTimestamp =  System.currentTimeMillis() / 1000;
long todayMidnightTimestamp = getMidnightTimestamp(currentTimestamp);