java 时区、日历和 SimpleDateFormat 的奇怪问题
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Strange problem with timezone, calendar and SimpleDateFormat
提问by Romain Linsolas
Let's consider the following code:
让我们考虑以下代码：
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss dd/MM/yyyy", Locale.US);
long start = sdf.parse("10:30:00 30/09/2009").getTime();
long end = sdf.parse("10:30:00 30/10/2009").getTime();
Calendar c = Calendar.getInstance(Locale.US);
c.setTimeInMillis(start);
System.out.println("Start = " + c.getTime());
c.setTimeInMillis(end);
System.out.println(" End = " + c.getTime());
When running this code snippet, I have the following output:
运行此代码片段时，我有以下输出：
Start = Wed Sep 30 10:30:00 CEST 2009
End = Fri Oct 30 10:30:00 CET 2009
Why do I get different timezone ?
为什么我得到不同的时区？
Note that if I set the first date in august and the second one in september, the output will display the same timezone in both cases:
请注意，如果我将第一个日期设置为 8 月，将第二个日期设置为 9 月，则输出将在两种情况下显示相同的时区：
long start = sdf.parse("10:30:00 30/08/2009").getTime();
long end = sdf.parse("10:30:00 30/09/2009").getTime();
will display:
将显示：
Start = Sun Aug 30 10:30:00 CEST 2009
End = Wed Sep 30 10:30:00 CEST 2009
I'm using Java 1.6.0_14
我正在使用 Java 1.6.0_14
回答by kgiannakakis
CESTis Central European Summer Time. It is the same as CETwith daylight savings into effect.
CEST是中欧夏令时。这CET与夏令时生效相同。
回答by user85421
You can set the default time zone
您可以设置默认时区
import java.util.TimeZone;
...
TimeZone.setDefault(TimeZone.getTimeZone("UTC")); // or "Etc/GMT-1"
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss dd/MM/yyyy", Locale.US);
long start = sdf.parse("10:30:00 30/09/2009").getTime();
long end = sdf.parse("10:30:00 30/10/2009").getTime();
Calendar c = Calendar.getInstance(Locale.US);
c.setTimeInMillis(start);
System.out.println("Start = " + c.getTime());
c.setTimeInMillis(end);
System.out.println(" End = " + c.getTime());
use TimeZone.getAvailableIDs()to see all available IDs.
用于TimeZone.getAvailableIDs()查看所有可用的 ID。
EDIT: you can also use a new SimpleTimeZone
编辑：您还可以使用新的 SimpleTimeZone
TimeZone.setDefault(new SimpleTimeZone(60 * 60 * 1000, "CET"));
回答by nanda
Yes, it is related to the daylight saving time. If you use a time zone that recognizes DST, it will be automatically used. You can use GMT for example if you don't want this.
是的，这与夏令时有关。如果您使用可识别 DST 的时区，它将自动使用。例如，如果您不想要这个，您可以使用 GMT。
