java 根据当前时区与东部时区的时差更改 LocalDateTime
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Changing LocalDateTime based on time difference in current time zone vs. eastern time zone
提问by yalpsid eman
Let's say one week ago I generate a LocalDateTime of 2015-10-10T10:00:00. Furthermore, let's assume I generate my current time zone id as such
假设一周前我生成了 2015-10-10T10:00:00 的 LocalDateTime。此外，假设我生成了当前的时区 ID
TimeZone timeZone = TimeZone.getDefault();
String zoneId = timeZone.getId(); // "America/Chicago"
And my zoneId is "America/Chicago".
我的 zoneId 是“美国/芝加哥”。
Is there an easy way I can convert my LocalDateTime to one for the time zone id "America/New_York" (ie so my updated LocalDateTime would be 2015-10-10T11:00:00)?
有没有一种简单的方法可以将我的 LocalDateTime 转换为时区 ID“America/New_York”（即我更新的 LocalDateTime 将是 2015-10-10T11:00:00）？
More importantly, is there a way I can convert my LocalDateTime to eastern time (ie, to a time zone with zoneId "America/New_York") no matter what time zone I am in? I am specifically looking for a way to do this with any LocalDateTime object generated in the past, and not necessarily for the current time this instant.
更重要的是，有没有一种方法可以将我的 LocalDateTime 转换为东部时间（即转换为 zoneId“America/New_York”的时区），无论我在哪个时区？我正在专门寻找一种方法来使用过去生成的任何 LocalDateTime 对象来执行此操作，而不必针对当前时间立即执行此操作。
回答by Andreas
To convert a LocalDateTimeto another time zone, you first apply the original time zone using atZone(), which returns a ZonedDateTime, then convert to the new time zone using withZoneSameInstant(), and finally convert the result back to a LocalDateTime.
要将 a 转换LocalDateTime为另一个时区，首先使用 应用原始时区atZone()，返回 a ZonedDateTime，然后使用 转换为新时区withZoneSameInstant()，最后将结果转换回 a LocalDateTime。
LocalDateTime oldDateTime = LocalDateTime.parse("2015-10-10T10:00:00");
ZoneId oldZone = ZoneId.of("America/Chicago");
ZoneId newZone = ZoneId.of("America/New_York");
LocalDateTime newDateTime = oldDateTime.atZone(oldZone)
.withZoneSameInstant(newZone)
.toLocalDateTime();
System.out.println(newDateTime.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME));
2015-10-10T11:00:00
If you skip the last step, you'd keep the zone.
如果您跳过最后一步，您将保留该区域。
ZonedDateTime newDateTime = oldDateTime.atZone(oldZone)
.withZoneSameInstant(newZone);
System.out.println(newDateTime.format(DateTimeFormatter.ISO_DATE_TIME));
2015-10-10T11:00:00-04:00[America/New_York]
