在不同时区获取相同日期

Question

我有一个纪元秒的时间。从这个纪元时间创建了一个日期对象。

Date date = new Date(epochMilli);

假设日期是"23 Nov 2019 00:00:00"

现在，我只想获得不同时区的相同日期，例如 :]

日本时间：2019 年 11 月 23 日00:00:00

美国时间：2019 年 11 月 23 日00:00:00

我目前正在使用 LocalDateTime 或 ZonedDateTime。

但是当我转换到不同的区域时，时间也会改变。但我不想改变这个时间。

提前致谢。

Answer 1

不幸的是，您没有向我们展示您如何使用ZonedDateTime，因此以下示例可能涵盖的内容超出了您展示如何解析 millis 的范围，将结果日期时间从一个区域转换为其他区域以及如何使用不同区域解析日期时间：

public static void main(String[] args) {

    long epochMillis = 1574208000000L;
    
    // define a formatter to be used
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd MMM yyyy HH:mm:ss",
                                                        Locale.ENGLISH);

    // create an instant from the milliseconds
    Instant instant = Instant.ofEpochMilli(epochMillis);
    // and create some example time zones for later use
    ZoneId utc = ZoneId.of("UTC");
    ZoneId tokyo = ZoneId.of("Asia/Tokyo");
    ZoneId losAngeles = ZoneId.of("America/Los_Angeles");
    ZoneId chicago = ZoneId.of("America/Chicago");
    
    /*
     * Part 1: Getting the date time converted to different time zones
     */
    
    // use the instant to create a ZonedDateTime at a specific time zone, here: UTC
    ZonedDateTime utcZdt = instant.atZone(utc);

    // then take the UTC-ZonedDateTime as base for conversion to other time zones 
    ZonedDateTime asiaTokyoConvertedfromUtc = utcZdt.withZoneSameInstant(tokyo);
    ZonedDateTime americaLosAngelesConvertedfromUtc = utcZdt.withZoneSameInstant(losAngeles);
    ZonedDateTime americaChicagoConvertedfromUtc = utcZdt.withZoneSameInstant(chicago);

    // print the results
    System.out.println("#### 1574208000000L at UTC, converted to other zones ####");
    System.out.println("UTC time zone:\t\t\t\t" + utcZdt.format(dtf));
    System.out.println("JST (Japan/Tokyo) time zone:\t\t"
                        + asiaTokyoConvertedfromUtc.format(dtf));
    System.out.println("PST (USA/Los Angeles) time zone:\t"
                        + americaLosAngelesConvertedfromUtc.format(dtf));
    System.out.println("CST (USA/Chicago) time zone:\t\t"
                        + americaChicagoConvertedfromUtc.format(dtf));
    
    System.out.println();

    /*
     * Part 2: Getting the date time in different time zones
     */
    
    // use the instant to create a ZonedDateTime at Asia/Tokyo
    ZonedDateTime asiaTokyoFromMillis = instant.atZone(tokyo);

    // use the instant to create a ZonedDateTime at America/Los Angeles
    ZonedDateTime americaLosAngelesFromMillis = instant.atZone(losAngeles);

    // use the instant to create a ZonedDateTime at America/Chicago
    ZonedDateTime americaChicagoFromMillis = instant.atZone(chicago);

    // print the (expected) results, same as converted date times...
    System.out.println("#### 1574208000000L at different zones ####");
    System.out.println("UTC time zone:\t\t\t\t" + utcZdt.format(dtf));
    System.out.println("JST (Asia/Tokyo) time zone:\t\t"
                        + asiaTokyoFromMillis.format(dtf));
    System.out.println("PST (USA/Los Angeles) time zone:\t"
                        + americaLosAngelesFromMillis.format(dtf));
    System.out.println("CST (USA/Chicago) time zone:\t\t"
                        + americaChicagoFromMillis.format(dtf));
    
    System.out.println();
    
    /*
     * Part 3: How to parse the date time instead of millis
     */
    
    // provide a parseable date time String
    String dateTime = "23 Nov 2019 00:00:00";
    
    // parse it in each desired time zone
    ZonedDateTime utc23Nov2019 = LocalDateTime.parse(dateTime, dtf).atZone(utc);
    ZonedDateTime asiaTokyo23Nov2019 = LocalDateTime.parse(dateTime, dtf)
                                                    .atZone(tokyo);
    ZonedDateTime americaChicago23Nov2019 = LocalDateTime.parse(dateTime, dtf)
                                                         .atZone(losAngeles);
    ZonedDateTime americaLosAngeles23Nov2019 = LocalDateTime.parse(dateTime, dtf)
                                                            .atZone(chicago);

    // print the results, now you have the 23. Nov 2019 at 00:00:00 at each time zone
    System.out.println("#### \"23 Nov 2019 00:00:00\" at different zones ####");
    System.out.println("UTC time zone:\t\t\t\t" + utc23Nov2019.format(dtf));
    System.out.println("JST (Asia/Tokyo) time zone:\t\t"
                        + asiaTokyo23Nov2019.format(dtf));
    System.out.println("PST (USA/Los Angeles) time zone:\t"
                        + americaChicago23Nov2019.format(dtf));
    System.out.println("CST (USA/Chicago) time zone:\t\t"
                        + americaLosAngeles23Nov2019.format(dtf));
}

这个的输出是

#### 1574208000000L at UTC, converted to other zones ####
UTC time zone:                      20 Nov 2019 00:00:00
JST (Japan/Tokyo) time zone:        20 Nov 2019 09:00:00
PST (USA/Los Angeles) time zone:    19 Nov 2019 16:00:00
CST (USA/Chicago) time zone:        19 Nov 2019 18:00:00

#### 1574208000000L at different zones ####
UTC time zone:                      20 Nov 2019 00:00:00
JST (Asia/Tokyo) time zone:         20 Nov 2019 09:00:00
PST (USA/Los Angeles) time zone:    19 Nov 2019 16:00:00
CST (USA/Chicago) time zone:        19 Nov 2019 18:00:00

#### "23 Nov 2019 00:00:00" at different zones ####
UTC time zone:                      23 Nov 2019 00:00:00
JST (Asia/Tokyo) time zone:         23 Nov 2019 00:00:00
PST (USA/Los Angeles) time zone:    23 Nov 2019 00:00:00
CST (USA/Chicago) time zone:        23 Nov 2019 00:00:00

Answer 2

遗留 java.util.Date 不区分时区。它基本上是自 1970-1-1 0:00 以来以毫秒为单位测量的时间点。没有别的。

打印日期时，会使用您系统的默认区域设置和时区对其进行格式化。为了获得针对不同时区格式化的 java.util.Date 对象，您必须相应地配置 DateFormat。

Date pointInTime = new Date();
DateFormat dateFormat = DateFormat.getDateTimeInstance();
dateFormat.setTimeZone(TimeZone.getTimeZone("PST"));
System.out.println(dateFormat.format(pointInTime));
dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println(dateFormat.format(pointInTime));

使用较新的 LocalDate API，情况有所不同。之前的回答给出了丰富的例子。

在不同时区获取相同日期

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