如何显示Java中的夏令时开始后的时间差异？ [英] How to show the difference in time after the daylight saving started in Java?

问题描述

我想检查夏令时开始前后的时间差。我正在使用JVM，其中时区与DST WRT巴西时间存在一些问题。我看到的输出显示10月21日属于夏令时，这是错误的，因为夏令时从11月4日开始。我希望看到10月20日至10月21日之间的时差为1小时，由于JRE时区问题，我可以在我的应用程序中看到该时差。有什么办法可以通过程序来实现。

I wanted to check the difference in time before and after the daylight saving time started. I am using a JVM where timezone has some issue with DST WRT Brazilian time. I could see the output where it says that 21st October falls under DST, which is wrong as the daylight saving started on 4th of November. I would like to see the timing difference which is 1 Hour in between 20th of October and 21st of October, which I could see in my application because of JRE Timezone issue. Is there any way I can achieve this by a program. Here below the code I have used to see if the date is under DST or not.

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
public class Timezone
{
    public static void main(String[] args) throws ParseException {
        TimeZone TIMEZONE = TimeZone.getTimeZone("Brazil/East");

        System.out.println("timeZone : " + TIMEZONE);
        Calendar c = Calendar.getInstance(TIMEZONE);
        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
        dateFormat.setTimeZone(TIMEZONE);

        Date date = dateFormat.parse("2018-10-20T00:00:00");
        c.setTime(date);
        System.out.println("In dst " + c.getTimeZone().inDaylightTime(c.getTime()));

        date = dateFormat.parse("2018-10-21T00:00:00");
        c.setTime(date);

        System.out.println("In dst " + c.getTimeZone().inDaylightTime(c.getTime()));

        date = dateFormat.parse("2018-11-04T00:00:00");
        c.setTime(date);
        System.out.println("In dst " + c.getTimeZone().inDaylightTime(c.getTime()));

    }
}

除了我的问题，我还能够找出夏令时是通过使用我的上述程序进行的。我想告诉我什么：10月20日时间是上午9点，而由于夏令时造成的同一时间偏移了1小时，即上午10点。有什么方法可以实现？

Adding further to my question I was able to figure out that daylight saving is applied by using my above program. I would like something where it should show me: On 20th October time is 9 am whereas same time due to DST shifted by 1 hr, i.e., 10 am. Is there any way to achieve this?

预期输出：

     timeZone : sun.util.calendar.ZoneInfo[id="Brazil/East"]

         Time is: 21-10-2018 07:52:16

实际输出错误的JVM：

        timeZone : timeZone : sun.util.calendar.ZoneInfo[id="Brazil/East"]

       Time is: 21-10-2018 08:52:30

推荐答案

我将添加一个简短的答案。它表明1天不等于24小时，即DST已更改。我还使用Java 8，因为我对Java 8更加熟悉。

I'll add a very brief answer. It shows that 1 day is not equal to 24 hours, i.e. DST changed. I also stepped over to Java 8 because I'm more familiar with it.

ZoneId timezone = ZoneId.of("Brazil/East");

ZonedDateTime t = ZonedDateTime.of(2018, 10, 20, 7, 52, 16, 0, timezone);

System.out.println(t);
System.out.println(t.plus(1, ChronoUnit.DAYS));
System.out.println(t.plus(24, ChronoUnit.HOURS));

输出：

2018-10- 20T07：52：16-03：00 [巴西/东部]

2018-10-21T 07 ：52：16-02：00 [巴西/东部]

2018-10-21T 08 ：52：16-02：00 [巴西/东部]

2018-10-20T07:52:16-03:00[Brazil/East]
2018-10-21T07:52:16-02:00[Brazil/East]
2018-10-21T08:52:16-02:00[Brazil/East]

这篇关于如何显示Java中的夏令时开始后的时间差异？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！