在 Java 或 Groovy 中转换 UTC 时间 T0 本地时间
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Convert UTC Time T0 Local Time In Java or Groovy
提问by maaz
i need to store createdOn (One Of the Attribute in Domain Class) . i am getting the system time and storing the value for this attribute.. My Time zone is (GMT+5:30 Chennai, Kolkata,Mumbai, New Delhi ) when i upload to the server it stores UTC time . I want it to be IST (Indian Standard Time) My Application Uses Groovy on Grails. Please Help me to adjust UTC /IST Time Difference. Thanks In advance
我需要存储 createdOn （域类中的属性之一）。我正在获取系统时间并存储此属性的值.. 我的时区是 (GMT+5:30 Chennai, Kolkata, Mumbai, New Delhi) 当我上传到它存储 UTC 时间的服务器时。我希望它是 IST（印度标准时间）我的应用程序在 Grails 上使用 Groovy。请帮我调整UTC /IST时差。提前致谢
回答by paxdiablo
No, don't do that. Ever!
不，不要那样做。曾经！
If you storetimes in local form, you're in for a world of pain. You basically have to store both the local time and the local timezone and the display of the time then becomes a complex beast (working out the source and target timezones).
如果您以本地形式存储时间，您将陷入痛苦的世界。您基本上必须同时存储本地时间和本地时区，然后时间的显示就变成了一个复杂的野兽（计算出源时区和目标时区）。
All times should be storedas UTC. No exception. Times entered by a user should be converted to UTC before being written anywhere (as soon as possible).
所有时间都应存储为 UTC。没有例外。用户输入的时间应在写入任何地方之前（尽快）转换为 UTC。
Times to be shown to a user should be converted from UTC to local as late as possible.
向用户显示的时间应尽可能晚地从 UTC 转换为本地时间。
Take this advice from someone who once got bogged down in the multi-timezone quagmire. Using UTC and converting only when necessary will make your life a lot easier.
从曾经陷入多时区泥潭的人那里得到这个建议。使用 UTC 并仅在必要时进行转换将使您的生活更轻松。
Once you have the UTC time, it's a matter of using the SimpleDateFormatclass to convert it:
获得 UTC 时间后，就可以使用SimpleDateFormat类来转换它了：
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class scratch {
public static void main (String args[]) {
Date now = new Date();
SimpleDateFormat sdf = new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss");
sdf.setTimeZone (TimeZone.getTimeZone ("IST"));
System.out.println ("Time in IST is " + sdf.format (now));
}
}
This outputs:
这输出：
Time in IST is 2011-04-11 13:40:04
which concurs with the current time in Mirzapur, which I think is where IST is based (not that it matters in India at the moment since it only has one timezone).
这与Mirzapur的当前时间一致，我认为这是 IST 的所在地（目前在印度并不重要，因为它只有一个时区）。
回答by Dead Programmer
SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
sf.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println(sf.format(new Date()));
SimpleDateFormat sf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
sf1.setTimeZone(TimeZone.getTimeZone("Asia/Calcutta"));
System.out.println(sf1.format(new Date()));
System.out.println(Arrays.asList(TimeZone.getDefault()));
