datetime - Java Time Zone When Parsing DateFormat

Question

I had code that parses date as follows:

String ALT_DATE_TIME_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSSZ";
SimpleDateFormat sdf = new SimpleDateFormat(
                    ALT_DATE_TIME_FORMAT);
Date date = sdf.parse(requiredTimeStamp);

And it was working fine, suddenly, this stopped working. It turns out an admin made some config changes on the server and the date is currently being returned as "2010-12-27T10:50:44.000-08:00" which is not parse-able by the above pattern. I have two questions:

The first would be what pattern would parse the date being returned by the JVM in the format above (specifically, just '-08:00' as the time zone)? And second, where exactly would one change such settings on a linux RHEL 5 server so that we are aware of such changes in the future?

Answer 1

tl;dr

OffsetDateTime.parse( "2010-12-27T10:50:44.000-08:00" )

ISO 8601

The input string format is defined in the ISO 8601 standard, a family of date-time formats.

Avoid old date-time classes

The Question and other Answers use old outmoded date-time classes bundled with the earliest versions of Java. Avoid them. Now supplanted by the java.time classes.

Using java.time

Your input string ends with an offset-from-UTC. So we parse as a OffsetDateTime object.

The java.time classes use ISO 8601 formats by default when parsing/generating strings. So no need to specify a formatting pattern.

OffsetDateTime odt = OffsetDateTime.parse( "2010-12-27T10:50:44.000-08:00" );

If you want to view this date-time value as a moment on the timeline in UTC, extract an Instant.

Instant instant = odt.toInstant();

A time zone is an offset plus a set of rules for handling anomalies such as Daylight Saving Time (DST). If you have a time zone in mind, apply a ZoneId to get a ZonedDateTime object. Same moment on the timeline, but viewed through a different wall-clock time.

ZoneId z = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt = odt.atZoneSameInstant( z );  // Same moment on the timeline, but viewed through a different wall-clock time.

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About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.