Java 如何将 UTC 毫秒转换为 UTC 日期 [英] Java How to convert UTC milliseconds into UTC Date

问题描述

我有一个 int 1446159600，它是 UTC/GMT 日期，2015 年 10 月 29 日星期四 23:00:00 GMT.我尝试转换为实际的 UTC 日期，但无法使其与 Calendar、SimpleDateFormat 和 Timezone 类一起使用.有人可以帮我吗?

解决方案

to;dr

Instant.ofEpochSecond ( 1_446_159_600L )

<块引用>

2015-10-29T23:00:00Z

从纪元开始计数

您似乎有一个整数 count-from-epoch 计算整秒在 Unix 时间 的时代，UTC.

您引用的旧日期时间类基于毫秒.所以乘以1000.

java.time

更好的是，完全避免那些旧类.新的 java.time 框架在 Java 8 及更高版本中是一个巨大的改进，取代了那些旧类.请参阅教程.这些新类的分辨率为纳秒，即几分之一秒内的 9 个小数位.

即时 类(UTC 时间线上的一个时刻)甚至有一个方便的 ofEpochSecond 方法，所以不需要乘以一千.

long wholeSecondsFromEpochInUtc = 1_446_159_600L;Instant Instant = Instant.ofEpochSecond ( wholeSecondsFromEpochInUtc );

这可以解决您的问题.

格式化

我们可以走得更远.将时区应用于该 Instant 以获得 ZonedDateTime.

ZoneId zoneId = ZoneId.of ( "America/Montreal" );ZonedDateTime zdt = ZonedDateTime.ofInstant ( instant , zoneId );DateTimeFormatter 格式化程序 = DateTimeFormatter.ofLocalizedDateTime ( FormatStyle.FULL ).withLocale ( Locale.CANADA_FRENCH );字符串输出 = zdt.format ( formatter );

转储到控制台.

System.out.println ( "即时 (UTC): " + 即时 );System.out.println("zdt:" + zdt);System.out.println("输出:" + 输出);

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即时 (UTC):2015-10-29T23:00:00Z

zdt: 2015-10-29T19:00-04:00[美国/蒙特利尔]

输出:jeudi 29 octobre 2015 19 h 00 EDT

I have an int 1446159600 which is UTC/GMT date Thu, 29 Oct 2015 23:00:00 GMT. I tried to do conversion to the actual UTC date, but couldn't get it to work with Calendar, SimpleDateFormat, and Timezone classes. Can someone help me?

解决方案

to;dr

Instant.ofEpochSecond ( 1_446_159_600L )

2015-10-29T23:00:00Z

Count From Epoch

You appear to have an integer count-from-epoch counting whole seconds with an epoch of Unix time, the first moment of 1970 in UTC.

The old date-time classes you reference are based on milliseconds. So multiply by 1,000.

java.time

Even better, avoid those old classes altogether. The new java.time framework in Java 8 and later is a vast improvement, supplanting those old classes. See Tutorial. These new classes have a resolution of nanoseconds, or 9 decimal places in a fraction of a second.

The Instant class (a moment on the timeline in UTC) even has a handy ofEpochSecond method, so no need to multiply by a thousand.

long wholeSecondsFromEpochInUtc = 1_446_159_600L;
Instant instant = Instant.ofEpochSecond ( wholeSecondsFromEpochInUtc );

That solves your Question in a one-liner.

Formatting

We can go further. Apply a time zone to that Instant to get a ZonedDateTime.

ZoneId zoneId = ZoneId.of ( "America/Montreal" );
ZonedDateTime zdt = ZonedDateTime.ofInstant ( instant , zoneId );
DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDateTime ( FormatStyle.FULL ).withLocale ( Locale.CANADA_FRENCH );
String output = zdt.format ( formatter );

Dump to console.

System.out.println ( "instant (UTC): " + instant );
System.out.println ( "zdt: " + zdt );
System.out.println ( "output: " + output );

instant (UTC): 2015-10-29T23:00:00Z

zdt: 2015-10-29T19:00-04:00[America/Montreal]

output: jeudi 29 octobre 2015 19 h 00 EDT

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