使用“ Z”字面值解析日期

我正在尝试解析一个看起来像这样的日期:

2010-04-05 T17:16:00Z

这是每个 http://www.ietf.org/rfc/rfc3339.txt的有效日期

如果我尝试使用 SimpleDateFormat 和这种模式解析它:

yyyy-MM-dd'T'HH:mm:ss

它将被解析为美国东部时间2010年4月5日星期一17:16:00


SimpleDateFormat无法用以下模式解析字符串:

yyyy-MM-dd'T'HH:mm:ssz
yyyy-MM-dd'T'HH:mm:ssZ

我可以显式地将 时区设置为在 SimpleDateFormat上使用,以获得预期的输出,但是我认为这没有必要。我是不是遗漏了什么?有其他日期解析器吗?

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The time zone should be something like "GMT+00:00" or 0000 in order to be properly parsed by the SimpleDateFormat - you can replace Z with this construction.

In the pattern, the inclusion of a 'z' date-time component indicates that timezone format needs to conform to the General time zone "standard", examples of which are Pacific Standard Time; PST; GMT-08:00.

A 'Z' indicates that the timezone conforms to the RFC 822 time zone standard, e.g. -0800.

I think you need a DatatypeConverter ...

@Test
public void testTimezoneIsGreenwichMeanTime() throws ParseException {
final Calendar calendar = javax.xml.bind.DatatypeConverter.parseDateTime("2010-04-05T17:16:00Z");
TestCase.assertEquals("gotten timezone", "GMT+00:00", calendar.getTimeZone().getID());
}

The restlet project includes an InternetDateFormat class that can parse RFC 3339 dates.

Restlet InternetDateFormat

Though, you might just want to replace the trailing 'Z' with "UTC" before you parse it.

Java doesn't parse ISO dates correctly.

Similar to McKenzie's answer.

Just fix the Z before parsing.

Code

String string = "2013-03-05T18:05:05.000Z";
String defaultTimezone = TimeZone.getDefault().getID();
Date date = (new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ")).parse(string.replaceAll("Z$", "+0000"));


System.out.println("string: " + string);
System.out.println("defaultTimezone: " + defaultTimezone);
System.out.println("date: " + (new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ")).format(date));

Result

string: 2013-03-05T18:05:05.000Z
defaultTimezone: America/New_York
date: 2013-03-05T13:05:05.000-0500

The date you are parsing is in ISO 8601 format.

In Java 7 the pattern to read and apply the timezone suffix should read yyyy-MM-dd'T'HH:mm:ssX

tl;dr

Instant.parse ( "2010-04-05T17:16:00Z" )

ISO 8601 Standard

Your String complies with the ISO 8601 standard (of which the mentioned RFC 3339 is a profile).

Avoid java.util.Date

The java.util.Date and .Calendar classes bundled with Java are notoriously troublesome. Avoid them.

Instead use either the Joda-Time library or the new java.time package in Java 8. Both use ISO 8601 as their defaults for parsing and generating string representations of date-time values.

java.time

The java.time framework built into Java 8 and later supplants the troublesome old java.util.Date/.Calendar classes. The new classes are inspired by the highly successful Joda-Time framework, intended as its successor, similar in concept but re-architected. Defined by JSR 310. Extended by the ThreeTen-Extra project. See the Tutorial.

The Instant class in java.time represents a moment on the timeline in UTC time zone.

The Z at the end of your input string means Zulu which stands for UTC. Such a string can be directly parsed by the Instant class, with no need to specify a formatter.

String input = "2010-04-05T17:16:00Z";
Instant instant = Instant.parse ( input );

Dump to console.

System.out.println ( "instant: " + instant );

instant: 2010-04-05T17:16:00Z

From there you can apply a time zone (ZoneId) to adjust this Instant into a ZonedDateTime. Search Stack Overflow for discussion and examples.

If you must use a java.util.Date object, you can convert by calling the new conversion methods added to the old classes such as the static method java.util.Date.from( Instant ).

java.util.Date date = java.util.Date.from( instant );

Joda-Time

Example in Joda-Time 2.5.

DateTimeZone timeZone = DateTimeZone.forID( "Europe/Paris" ):
DateTime dateTime = new DateTime( "2010-04-05T17:16:00Z", timeZone );

Convert to UTC.

DateTime dateTimeUtc = dateTime.withZone( DateTimeZone.UTC );

Convert to a java.util.Date if necessary.

java.util.Date date = dateTime.toDate();

The 'X' only works if partial seconds are not present: i.e. SimpleDateFormat pattern of

"yyyy-MM-dd'T'HH:mm:ssX"

Will correctly parse

"2008-01-31T00:00:00Z"

but

"yyyy-MM-dd'T'HH:mm:ss.SX"

Will NOT parse

"2008-01-31T00:00:00.000Z"

Sad but true, a date-time with partial seconds does not appear to be a valid ISO date: http://en.wikipedia.org/wiki/ISO_8601

I provide another answer that I found by api-client-library by Google

try {
DateTime dateTime = DateTime.parseRfc3339(date);
dateTime = new DateTime(new Date(dateTime.getValue()), TimeZone.getDefault());
long timestamp = dateTime.getValue();  // get date in timestamp
int timeZone = dateTime.getTimeZoneShift();  // get timezone offset
} catch (NumberFormatException e) {
e.printStackTrace();
}

Installation guide,
https://developers.google.com/api-client-library/java/google-api-java-client/setup#download

Here is API reference,
https://developers.google.com/api-client-library/java/google-http-java-client/reference/1.20.0/com/google/api/client/util/DateTime

Source code of DateTime Class,
https://github.com/google/google-http-java-client/blob/master/google-http-client/src/main/java/com/google/api/client/util/DateTime.java

DateTime unit tests,
https://github.com/google/google-http-java-client/blob/master/google-http-client/src/test/java/com/google/api/client/util/DateTimeTest.java#L121

With regards to JSR-310 another project of interest might be threetenbp.

JSR-310 provides a new date and time library for Java SE 8. This project is the backport to Java SE 6 and 7.

In case you are working on an Android project you might want to checkout the ThreeTenABP library.

compile "com.jakewharton.threetenabp:threetenabp:${version}"

JSR-310 was included in Java 8 as the java.time.* package. It is a full replacement for the ailing Date and Calendar APIs in both Java and Android. JSR-310 was backported to Java 6 by its creator, Stephen Colebourne, from which this library is adapted.

According to last row on the Date and Time Patterns table of the Java 7 API

X Time zone ISO 8601 time zone -08; -0800; -08:00

For ISO 8601 time zone you should use:

  • X for (-08 or Z),
  • XX for (-0800 or Z),
  • XXX for (-08:00 or Z);

so to parse your "2010-04-05T17:16:00Z" you can use either "yyyy-MM-dd'T'HH:mm:ssX" or "yyyy-MM-dd'T'HH:mm:ssXX" or "yyyy-MM-dd'T'HH:mm:ssXXX" .

    System.out.println(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssX").parse("2010-04-05T17:16:00Z"));
System.out.println(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXX").parse("2010-04-05T17:16:00Z"));
System.out.println(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXXX").parse("2010-04-05T17:16:00Z"));

will correctly print out 'Mon Apr 05 13:16:00 EDT 2010'

Under Java 8 use the predefined DateTimeFormatter.ISO_DATE_TIME

 DateTimeFormatter formatter = DateTimeFormatter.ISO_DATE_TIME;
ZonedDateTime result = ZonedDateTime.parse("2010-04-05T17:16:00Z", formatter);

I guess its the easiest way

Since java 8 just use ZonedDateTime.parse("2010-04-05T17:16:00Z")