将UTC日期转换为其他时区

问题描述

  SimpleDateFormat format = new SimpleDateFormat（yyyy -MM-ddHH：mm：ss）; 
 Date parsed = format.parse（2011-03-01 15:10:37）; 
 TimeZone tz = TimeZone.getTimeZone（America / Chicago）; 
 format.setTimeZone（tz）; 
 
 String result = format.format（parsed）; 
  

所以输入是 2011-03-01 15:10:37 ，但这个（结果值）的输出是 2011-03-01 05:40:37 。虽然看起来不错，根据，它应该是 2011-03-01 09:10:37 。

我做错了什么？

解决方案

事实证明，代码几乎正确，我没有考虑到的是在解析 String 最初获得 Date 对象，它使用默认系统 TimeZone ，所以源日期不在UTC正如我预期的那样。

诀窍是在将日期解析为UTC时设置时区，然后将其设置为目标 TimeZone 。这样的东西：

  SimpleDateFormat sourceFormat = new SimpleDateFormat（yyyy-MM-dd HH：mm：ss）; 
 sourceFormat.setTimeZone（TimeZone.getTimeZone（UTC））; 
日期解析= sourceFormat.parse（2011-03-01 15:10:37）; // =>日期在UTC现在
 
 TimeZone tz = TimeZone.getTimeZone（America / Chicago）; 
 SimpleDateFormat destFormat = new SimpleDateFormat（yyyy-MM-dd HH：mm：ss）; 
 destFormat.setTimeZone（tz）; 
 
 String result = destFormat.format（parsed）; 
  

I'm converting a UTC time to another timezone, using this method:

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date parsed = format.parse("2011-03-01 15:10:37");
TimeZone tz = TimeZone.getTimeZone("America/Chicago");
format.setTimeZone(tz);

String result = format.format(parsed);

So the input is 2011-03-01 15:10:37 but the output of this (value of result) is 2011-03-01 05:40:37. While it seems off, and according to this link, it should be 2011-03-01 09:10:37.

What am I doing wrong?

解决方案

It turns out the code was almost correct, what I didn't take into account was that when parsing the String to get a Date object initially, it uses default system TimeZone, so the source date was not in UTC as I expected.

The trick was to set the timezone when parsing the date to UTC and then set it to destination TimeZone. Something like this:

SimpleDateFormat sourceFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
sourceFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
Date parsed = sourceFormat.parse("2011-03-01 15:10:37"); // => Date is in UTC now

TimeZone tz = TimeZone.getTimeZone("America/Chicago");
SimpleDateFormat destFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
destFormat.setTimeZone(tz);

String result = destFormat.format(parsed);

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