Cannot parse String in ISO 8601 format, lacking colon in offset, to Java 8 Date

tl;dr

Until bug is fixed:

OffsetDateTime.parse( 
    "2018-02-13T10:20:12.120+0000" , 
    DateTimeFormatter.ofPattern( "uuuu-MM-dd'T'HH:mm:ss.SSSX" )
)

When bug is fixed:

OffsetDateTime.parse( "2018-02-13T10:20:12.120+0000" )

Details

You are using the wrong classes.

Avoid the troublesome old legacy classes such as Date, Calendar, and SimpleDateFormat. Now supplanted by the java.time classes.

The ZonedDateTime class you used is good, it is part of java.time. But it is intended for a full time zone. Your input string has merely an offset-from-UTC. A full time zone, in contrast, is a collection of offsets in effect for a region at different points in time, past, present, and future. For example, with Daylight Saving Time (DST) in most of North America, the offsets change twice a year growing smaller in the Spring as we shift clocks forward an hour, and restoring to a longer value in the Autumn when we shift clocks back an hour.

OffsetDateTime

For only an offset rather than a time zone, use the OffsetDateTime class.

Your input string complies with the ISO 8601 standard. The java.time classes use the standard formats by default when parsing/generating strings. So no need to specify a formatting pattern.

OffsetDateTime odt = OffsetDateTime.parse( "2018-02-13T10:20:12.120+0000" );

Well, that should have worked. Unfortunately, there is a bug in Java 8 (at least up through Java 8 Update 121) where that class fails to parse an offset omitting the colon between hours and minutes. So the bug bites on +0000 but not +00:00. So until a fix arrives, you have a choice of two workarounds: (a) a hack, manipulating the input string, or (b) define an explicit formatting pattern.

The hack: Manipulate the input string to insert the colon.

String input = "2018-02-13T10:20:12.120+0000".replace( "+0000" , "+00:00" );
OffsetDateTime odt = OffsetDateTime.parse( input );

DateTimeFormatter

The more robust workaround is to define and pass a formatting pattern in a DateTimeFormatter object.

String input = "2018-02-13T10:20:12.120+0000" ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu-MM-dd'T'HH:mm:ss.SSSX" );
OffsetDateTime odt = OffsetDateTime.parse( input , f );

odt.toString(): 2018-02-13T10:20:12.120Z

By the way, here is a tip: I have found that with many protocols and libraries, your life is easier if your offsets always have the colon, always have both hours and minutes (even if minutes are zero), and always use a padding zero (-05:00 rather than -5).

DateTimeFormatterBuilder

For a more flexible formatter, created via DateTimeFormatterBuilder, see this excellent Answer on a duplicate Question.

Instant

If you want to work with values that are always in UTC (and you should), extract an Instant object.

Instant instant = odt.toInstant();

ZonedDateTime

If you want to view that moment through the lens of some region’s wall-clock time, apply a time zone.

ZoneId z = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt = odt.atZoneSameInstant( z );

See this code run live at IdeOne.com.

All of this has been covered many times in many Answers for many Questions. Please search Stack Overflow thoroughly before posting. You would have discovered many dozens, if not hundreds, of examples.

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, Java SE 10, 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 (<26), 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.

Short: Not a bug, just your pattern is wrong.

Please use the type OffsetDateTime which is especially designed for time zone offsets and use a pattern this way:

OffsetDateTime odt =
    OffsetDateTime.parse( 
        "2018-02-13T10:20:12.120+0000" , 
        DateTimeFormatter.ofPattern( "uuuu-MM-dd'T'HH:mm:ss.SSSZZZ" )
    )

Problems in detail:

a) 12-hour-clock versus 24-hour-clock

"h" indicates the hour of AM/PM on a 12-hour-clock but you obviously need "H" for the 24-hour-clock as required by ISO-8601.

b) The form of zero offset

If you want to parse zero offset like "+0000" instead of "Z" (as described in ISO-paper) you should not use the pattern symbol "X" but "ZZZ". Citing the pattern syntax:

Offset Z: This formats the offset based on the number of pattern letters. One, two or three letters outputs the hour and minute, without a colon, such as '+0130'. The output will be '+0000' when the offset is zero.

c) Your input is NOT ISO-8601-compatible therefore no bug in Java

Your assumption that "2018-02-13T10:20:12.120+0000" shall be valid ISO is wrong because you are mixing basic format (in the offset part) and extended format which is explicitly prohibited in ISO-paper (see sections 4.3.2 (example part) and 4.3.3d). Citing ISO-8601:

[...]the expression shall either be completely in basic format, in which case the minimum number of separators necessary for the required expression is used, or completely in extended format[...]

The statement of B. Bourque that java.time has a bug is based on the same wrong expectation about ISO-compatibility. And the documentation of let's say ISO_OFFSET_DATE_TIME describes the support of the extended ISO-format only. See also the related JDK issue. Not all ISO-8601-variants are directly supported hence a pattern-based construction of the parser in the right way is okay.