我可以从不同区域的 LocalDateTime 获得正确的日期时间吗？

Question

我使用 LocalDateTime.now() 在数据库中保存了当前日期时间，我看到它被保存为键值的 Map，在地图中我看到时间、月、年、秒的键, 纳米——等等。但我看不到有关区域的信息。因此，如果在不同区域检索相同的时间日期，比如美国（从印度保存的数据），那么该怎么做？

Answer 1

Date date = new Date();
ZonedDateTime zonedDateTime = date.toInstant().atZone(ZoneId.of("US/Eastern"));

有不同的时区，根据它们的值你可以有日期时间。

Answer 2

LocalDateTime 与地点或时区无关

引用，查看关于 LocalDateTime 的 900+ upvotes 的答案：

They are not tied to any one locality or time zone. They are not tied to the timeline. They have no real meaning until you apply them to a locality to find a point on the timeline.

引用的更多内容，关于 java-time 类型用法：

So for business apps, the "Local" types are not often used as they represent just the general idea of a possible date or time not a specific moment on the timeline. Business apps tend to care about the exact moment an invoice arrived, a product shipped for transport, an employee was hired, or the taxi left the garage. So business app developers use Instant and ZonedDateTime classes most commonly.

以下是指定时区的推荐类型之一的示例“America/Los_Angeles”：

ZonedDateTime zonedDateTime = ZonedDateTime.now(ZoneId.of("America/Los_Angeles"));

这是做同样事情的另一种变体：

ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(Instant.now(), ZoneId.of("America/Los_Angeles"));

另一个做同样事情的变体：

ZonedDateTime zonedDateTime = ZonedDateTime.now().withZoneSameInstant(ZoneId.of("America/Los_Angeles"));

您可以使用 ZoneId.getAvailableZoneIds():

查看可用区域 ID

ZoneId.getAvailableZoneIds().stream().forEach(System.out::println);

了解更多关于 java.time 的信息：

，查看 900+ 赞的答案。

您可以在此处阅读有关 ZonId 和 ZoneOffset 的更多信息： https://docs.oracle.com/javase/10/docs/api/java/time/ZoneId.html https://docs.oracle.com/javase/10/docs/api/java/time/ZoneOffset.html

Answer 3

如overview of modern date-time classes in Java所示，有time-zone信息的class有ZonedDateTime、OffsetDateTime、OffsetTime等。 class、LocalDateTime没有time-zone信息。

如前所述here,

The class that handles both date and time, without a time zone, is LocalDateTime, one of the core classes of the Date-Time API. This class is used to represent date (month-day-year) together with time (hour-minute-second-nanosecond) and is, in effect, a combination of LocalDate with LocalTime. This class can be used to represent a specific event, such as the first race for the Louis Vuitton Cup Finals in the America's Cup Challenger Series, which began at 1:10 p.m. on August 17, 2013. Note that this means 1:10 p.m. in local time. To include a time zone, you must use a ZonedDateTime or an OffsetDateTime, as discussed in Time Zone and Offset Classes.

下面给出了使用 OffsetDateTime:

的示例代码

OffsetDateTime odt = OffsetDateTime.now(ZoneOffset.UTC);// Change ZoneOffset as applicable
PreparedStatement st = conn.prepareStatement("INSERT INTO mytable (columnfoo) VALUES (?)");
st.setObject(1, odt);
st.executeUpdate(); 
st.close();

在 Trail: Date Time.

了解有关现代 date-time API 的更多信息

我可以从不同区域的 LocalDateTime 获得正确的日期时间吗？

Can I get correct datetime from LocalDateTime in defferent zone?

java

timezone

java-time

timezone-offset

zoneddatetime