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How to achive this date format in calendar

I have to create the XMLGregorianCalendar object with this date format "YYYY-MM-DDTHH:MI:SS±TZ" e.g. "2015-07-01T17:42:49+04"
I have no idea how to do this. I've used a number of ways on how to convert date, but this pattern doesn't seem to work.
After some experiments I found that "YYYY-MM-dd'T'HH:mm:ssX" will give me the desired output. But it's a string and I can't achieve the same format with XMLGregorianCalendar.
It gives me "2015-07-01T17:42:4234+05:00", as you see there're additional symbols that i don't need.

Date-time objects have no format
XMLGregorianCalendar object with this date format
Date-time objects such as XMLGregorianCalendar do not have a “format”. They internally represent the date-time value in some manner, though not likely to be in text.
You can instantiate date-time objects by parsing text. And your date-time objects can generate text representing their internal value. But the text and the date-time object are distinct and separate from one another.
java.time
The XMLGregorianCalendar class is now obsolete. Supplanted by the modern java.time classes defined in JSR 310.
Parse your input string as a OffsetDateTime as in includes an offset-from-UTC but not a time zone.
OffsetDateTime odt = OffsetDateTime.parse( "2015-07-01T17:42:49+04" );
Generate text in standard ISO 8601 format.
String output = odt.toString() ; // Generates text in ISO 8601 format.
2015-07-01T17:42:49+04:00
Parts of an offset
The part at the end is the offset-from-UTC, a number of hours-minutes-seconds ahead or behind the prime meridian. In ISO 8601, the Plus sign is a positive number that means ahead of UTC. A Minus sign is a negative number that means behind UTC.
Suppressing parts of an offset
Some people may drop the seconds when zero, or drop the minutes when zero. But suppressing those digits does not change the meaning. These three strings all represent the very same moment:
2015-07-01T17:42:49+04
2015-07-01T17:42:49+04:00
2015-07-01T17:42:49+04:00:00
You said:
"2015-07-01T17:42:4234+05:00", as you see there're additional symbols that i don't need.
[I assume you really meant "2015-07-01T17:42:49+04:00" but made typos.]
You really should not care about this. Indeed, I recommend you always include both the hours and the minutes as I have seen multiple libraries/protocols that expect both hours and minutes, breaking if omitted. While the minutes and seconds are indeed optional in ISO 8601 when their value is zero, I suggest you always include the minutes when zero.
DateTimeFormatter
If you insist otherwise, you will need to use DateTimeFormatter class, and possibly DateTimeFormatterBuilder, to suppress the minutes when zero. Perhaps this:
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu-MM-dd'T'HH:mm:ssx" );
String output = odt.format( f );
2015-07-01T17:42:49+04
The x code in that formatting pattern suppressed the minutes, and seconds, if their value is zero.
If doing your own formatting, be sure to not truncate when non-zero, or your result will be a falsehood (a different moment). Take for example, representing this moment as seen in India where current the offset in use is five and half hours (an offset that includes 30 minutes rather than zero).
ZoneId z = ZoneId.of( "Asia/Kolkata" );
ZonedDateTime zdt = odt.atZoneSameInstant( z );
OffsetDateTime odtKolkata = zdt.toOffsetDateTime();
Dump to console.
System.out.println( "odtKolkata = " + odtKolkata );
2015-07-01T19:12:49+05:30
XMLGregorianCalendar
If you absolutely must use the old legacy class XMLGregorianCalendar, you can create one from the ISO 8601 output of our OffsetDateTime object seen in code above. See this Answer on another Question.
XMLGregorianCalendar xgc = null;
try
{
xgc = DatatypeFactory.newInstance().newXMLGregorianCalendar( odt.toString() );
}
catch ( DatatypeConfigurationException e )
{
e.printStackTrace();
}
System.out.println( "xgc.toString(): " + xgc );
xgc.toString(): 2015-07-01T17:42:49+04:00
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.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
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, Java SE 11, and later - 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
Most 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….

XMLGregorianCalendar date format 'dd/MM/yyyy HH:mm:ss.SSS'

String formatA ="yyyy-MM-dd'T'HH:mm:ss'Z'";
String formatB = "dd/MM/yyyy HH:mm:ss.SSS";
try {
XMLGregorianCalendar gregFmt = DatatypeFactory.newInstance().newXMLGregorianCalendar(new SimpleDateFormat(formatB).format(new Date()));
System.out.println(gregFmt);
} catch (DatatypeConfigurationException e) {
};
I am trying to formate XMLGregorianCalendar date .
The above code formats well for format "yyyy-MM-dd'T'HH:mm:ss'Z'"
But for formatB dd/MM/yyyy HH:mm:ss.SSS it throws error
java.lang.IllegalArgumentException
Do advice on how to fix it. Thank you so much!
log
Exception in thread "main" java.lang.IllegalArgumentException: 23/08/2017 16:13:04.140
at com.sun.org.apache.xerces.internal.jaxp.datatype.XMLGregorianCalendarImpl$Parser.parseAndSetYear(XMLGregorianCalendarImpl.java:2887)
at com.sun.org.apache.xerces.internal.jaxp.datatype.XMLGregorianCalendarImpl$Parser.parse(XMLGregorianCalendarImpl.java:2773)
at com.sun.org.apache.xerces.internal.jaxp.datatype.XMLGregorianCalendarImpl.<init>(XMLGregorianCalendarImpl.java:435)
at com.sun.org.apache.xerces.internal.jaxp.datatype.DatatypeFactoryImpl.newXMLGregorianCalendar(DatatypeFactoryImpl.java:536)
at test.test.main(test.java:19)
line19 is line 4 , in the above code 'XMLGregorianCalendar gregFmt...'

The format that newXMLGregorianCalendar(string) accept is described in the XML specs and is different from the formatB you are trying to use.

tl;dr
Date-time objects do not have a “format”. They parse & generate String objects representing textually their value.
Use the modern java.time that replaced terrible old classes Date & XMLGregorianCalendar classes.
Example:
myXMLGregorianCalendar // If you must use this class… but try to avoid. Use *java.time* classes instead.
.toGregorianCalendar() // Converting from `javax.xml.datatype.XMLGregorianCalendar` to `java.util.GregorianCalendar`.
.toZonedDateTime() // Converting from `java.util.GregorianCalendar` to `java.time.ZonedDateTime`, from legacy class to modern class.
.format( // Generate a `String` representing the moment stored in our `ZonedDateTime` object.
DateTimeFormatter.ofPattern( "dd/MM/uuuu HH:mm:ss.SSS" ) // Define a formatting pattern as you desire. Or better, automatically localize by calling `DateTimeFormatter.ofLocalized…` methods.
) // Returns a `String` object, distinct from our `ZonedDateTime` object.
07/07/2018 15:20:14.372
Date-time objects do not have a format
Do not conflate date-time objects with the strings they generate to represent their value. Date-time values, including the classes discussed below, are not a String, do not use text as their internal value, and do not have a “format”. All of them can generate, and parse, strings to represent their date-time value.
java.time
The modern approach uses the java.time classes that supplanted the troublesome old legacy date-time classes such as XMLGregorianCalendar.
The use of java.util.Date should be replaced with java.time.Instant. Both represent a moment in UTC. Instant uses a finer resolution of nanoseconds rather than milliseconds.
You can easily convert between the modern and legacy classes. Notice the new conversion methods added to the old classes, in this case java.util.GregorianCalendar::toZonedDateTime.
First convert from javax.xml.datatype.XMLGregorianCalendar to java.util.GregorianCalendar.
GregorianCalendar gc = myXMLGregorianCalendar.toGregorianCalendar() ;
Now get out of these legacy classes, and into java.time.
ZonedDateTime zdt = gc.toZonedDateTime() ;
All three types so far, the XMLGregorianCalendar, the GregorianCalendar, and the ZonedDateTime all represent the same moment, a date with time-of-day and an assigned time zone.
With a ZonedDateTime in hand, you can generate a String in standard ISO 8601 format extended to append the name of the time zone in square brackets.
String output = zdt.toString() ; // Generate string in standard ISO 8601 format extended by appending the name of time zone in square brackets.
2018-07-07T15:20:14.372-07:00[America/Los_Angeles]
You can generate strings in other formats using DateTimeFormatter class. For the formatting pattern listed second in your question, define a matching DateTimeFormatter object.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd/MM/uuuu HH:mm:ss.SSS" ) ;
String output = zdt.format( f ) ;
07/07/2018 15:20:14.372
The first formatting pattern listed in your Question has a Z on the end, which means UTC and is pronounced “Zulu”. To adjust our ZonedDateTime to UTC, simply extract a Instant object. An Instant is always in UTC by definition.
Instant instant = zdt.toInstant() ; // Extract an `Instant` object, always in UTC.
Generate a String in the pattern shown first in the Question.
String output = instant.toString() ; // Generate string in standard ISO 8601 format.
2018-07-07T22:20:14.372Z
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.

Parsing ISO 8601 date format like 2015-06-27T13:16:37.363Z in Java [duplicate]

This question already has answers here:
Java / convert ISO-8601 (2010-12-16T13:33:50.513852Z) to Date object
(4 answers)
Closed 6 years ago.
I am trying to parse a String using SimpleDateFormat.
This is my current code:
public String getCreatedDateTime() {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-ddEHH:mm:ss.zzzz");
try {
Date date = simpleDateFormat.parse("2015-06-27T13:16:37.363Z");
return date.toString();
} catch (ParseException e) {
return "Error parsing date";
}
}
As you can see, I just put a constant in the parse() method for testing purposes.
So, this is what I am trying to parse:
2015-06-27T13:16:37.363Z
This is the SimpleDateFormat pattern that I am using:
yyyy-MM-ddEHH:mm:ss.zzzz
I keep getting the ParseException.
I know that it is proably because of the .zzzz at the end but I have no idea what .363Z might stand for so I just used some random letters. Bad idea.
I'll appreciate your help a lot. Thank you!

Try with this pattern (note the X at the end and the 'T' in the middle):
"yyyy-MM-dd'T'HH:mm:ss.SSSX"
From Java's SimpleDateFormat's documentation:
ISO 8601 Time zone:
...
For parsing, "Z" is parsed as the UTC time zone designator.
And, from the part where it describes the different characters:
X - Time zone - ISO 8601 time zone
EDIT
If using Android, then "X" is not supported.
You can use this pattern (note Z is a literal now):
"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
But then you'll get the date on your current timezone and would need to convert it to UTC if needed.

tl;dr
Skip the formatting pattern. Standard ISO 8601 format is used by default.
Instant.parse( "2015-06-27T13:16:37.363Z" )
ISO 8601
Your string format is formally defined by the ISO 8601 standard.
Basically your Question is a duplicate of this one, Converting ISO 8601-compliant String to java.util.Date.
Alternatives
The Answer by eugenioy is correct.
But you should know that the old java.util.Date/.Calendar/java.text.SimpleDateFormat classes bundled with Java are notoriously troublesome and should be avoided.
Outmoded Classes
Those old classes are now outmoded, first by the third-party Joda-Time library, and now by the new java.time package (Tutorial) built into Java 8 and later (inspired by Joda-Time, defined by JSR 310, extended by the ThreeTen-Extra project).
Both java.time and Joda-Time use the ISO 8601 standard as their defaults when parsing/generating string representations of date-time values. So the code is simple, no need for custom formatter objects. No need for all that format twiddling that caused your Exception.
Time Zone
Both java.time and Joda-Time have a zoned date-time class that understands its assigned time zone (unlike java.util.Date). If you do not assign one, the JVM’s current default time zone is assigned.
Beware that the JVM’s current default time zone can change at any time. It can change at deployment, defaulting to whatever the host OS setting is. And it can change at any moment during runtime when any code in any thread of any app within the JVM calls TimeZone.setDefault. So better to explicitly assign a desired/expected time zone.
java.time
The Z on the end of your string is short for Zulu and means UTC. The Instant class can directly parse that format, to represent a moment on the timeline in UTC with a resolution in nanoseconds.
String input = "2015-06-27T13:16:37.363Z";
Instant instant = Instant.parse( input );
Change the time zone from UTC to some desired/expected time zone.
ZoneID zone = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime zdtMontréal = instant.atZone( zone ) ;
If you really need a java.util.Date for interoperability, convert.
java.util.Date utilDate = Date.from( zdtMontréal.toInstant() ) ;
Joda-Time
The Joda-Time project is now in maintenance mode, with the team advising migration to the java.time classes:
Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.
Example code using Joda-Time 2.8.1.
String input = "2015-06-27T13:16:37.363Z" ;
DateTimeZone zone = DateTimeZone.UTC ; // Or: DateTimeZone.forID( "America/Montreal" ) ;
DateTime dateTime = new DateTime( input, zone ) ;
If you really need a java.util.Date for interoperability, convert.
java.util.Date date = dateTime.toDate();
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.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
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, Java SE 11, and later - 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
Most 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.

Formatting ISO 8601 date with a colon seperator

I am trying to convert the date in milliseconds to the following ISO 8601 format:
But I am getting the following using SimpleDateFormat:
/**
* It converts the time from long to the ISO format
*
* #param timestampMillis
* #return isoDate
*/
public String convertTimeMillisToISO8601(String timestampMillis)
{
long timeInLong= Long.parseLong(timestampMillis);
DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");
df.setTimeZone(TimeZone.getTimeZone("UTC"));
String isoDate = df.format(new java.util.Date(timeInLong));
return isoDate;
}
OUTPUT:
"ts":"2015-06-18T09:56:21+0000"
I know I can use substring to append the extra colon but Is there any better way to do so ?

For Java 7 and higher, you might use XXX (ISO 8601 time zone) in the date format String. According to the documentation, the result of X can be:
X => -08
XX => -0800
XXX => -08:00
but for all of those, it might as well return Z!
For Java 6 and earlier, there is no X (J6 doc), and since the result of X may or may not do what you want, I strongly recommend you just insert that colon yourself.

You can always use a StringBuilder:
new StringBuilder(
new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
.format(date))
.insert(22,':')
.toString();

For Java 8 if you use one of the standard ISO_DATE_* format patterns then the output formatted String will be truncated when the offset is +00:00 (UTC typically just appends Z).
OffsetDateTime utcWithFractionOfSecond = ZonedDateTime.parse("2018-01-10T12:00:00.000000+00:00", DateTimeFormatter.ISO_OFFSET_DATE_TIME);
utcWithFractionOfSecond.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME); // 2018-01-10T12:00:00Z ... not what you want!
The only solution I have found is using the outputPattern (shown below) that uses lowercase `xxx' to ensure that a colon is included in the timezone offset.
I have included an example with factions-of-a-second for completeness (you can remove the SSSSSS in your case)
DateTimeFormatter inputPattern = DateTimeFormatter.ISO_OFFSET_DATE_TIME;
DateTimeFormatter outputPattern = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSSSSxxx");
OffsetDateTime utcWithFractionOfSecond = OffsetDateTime.parse("2018-01-10T12:00:00.000000+00:00", inputPattern);
OffsetDateTime utcNoFractionOfSecond = OffsetDateTime.parse("2018-01-10T12:00:00+00:00", inputPattern);
OffsetDateTime utcWithZ = OffsetDateTime.parse("2018-01-10T12:00:00Z", inputPattern);
OffsetDateTime utcPlus3Hours = OffsetDateTime.parse("2018-01-10T12:00:00.000000+03:00", inputPattern);|
utcWithFractionOfSecond.format(outputPattern ); // 2018-01-10T12:00:00.000000+00:00
utcNoFractionOfSecond.format(outputPattern); // 2018-01-10T12:00:00.000000+00:00
utcWithZ.format(outputPattern); // 2018-01-10T12:00:00.000000+00:00
utcPlus3Hours.format(outputPattern); // 2018-01-10T12:00:00.000000+03:00
In these examples I have used ISO_OFFSET_DATE_TIME only to create the input values for the test cases. In all cases it is the outputPattern yyyy-MM-dd'T'HH:mm:ss.SSSSSSxxx that controlling how to include a colon character in the timezone portion of your resulting formatted string.
Note that if your input data included the Zone ID like [Europe/London] then you would create your input data using ZonedDateTime instead of OffsetDateTime

Can you use Java 8?
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("YYYY-MM-dd'T'HH:mm:ssXXX");
System.out.println(formatter.format(ZonedDateTime.now()));
2015-04-15T17:24:19+09:00

tl;dr
OffsetDateTime.parse( "2014-06-18T09:56:21+00:00" )
2014-06-18T09:56:21Z
Details
Some other answers are close, correct in using the modern java.time classes that supplanted the terrible old legacy classes (Date, Calendar, SimpleDateFormat). But they are either working too hard or chose the wrong class.
ISO 8601
Your format is in standard ISO 8601 format. The java.time classes use these standard formats by default when parsing/generating text representing their date-time values. So you need not specify any formatting pattern at all. Works by default.
OffsetDateTime
Your input indicates an offset-from-UTC of zero hours and zero minutes. So we should use the OffsetDateTime class.
String input = "2014-06-18T09:56:21+00:00";
OffsetDateTime odt = OffsetDateTime.parse( input );
Zulu time
We can generate a string in standard ISO 8601 format by merely calling toString. The Z on the end means UTC, and is pronounced “Zulu”.
odt.toString(): 2014-06-18T09:56:21Z
ZonedDateTime
If your input indicated a time zone, rather than merely an offset, we would have used ZonedDateTime class. An offset is simply a number of hours, minutes, and seconds – nothing more. A time zone is much more. A time zone is a history of past, present, and future changes to the offset used by the people of a particular region.
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, Java SE 11, and later - 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
Most 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.

Convert current date & time to equivalent GMT date & time

I used the below code where I've printed the modified GMT date in String & in Date format, it's giving me two different values.
Date initial = new Date();
DateFormat dateFormatter = DateFormat.getInstance();
dateFormatter.setTimeZone (TimeZone.getTimeZone("UTC"));
String gmtS = dateFormatter.format(initial);
Date gmt = dateFormatter.parse(gmtS);
System.out.println("Data type is Date = " + gmt);
System.out.println("Data type is String "+gmtS);
Output
gtm where value id of type Date = Thu Jul 03 23:15:00 EDT 2014
gmtS where value id of type String = 7/4/14 3:15 AM
But I want to see the value (7/4/14 3:15 AM) as a Date type.
Any help is really appreciated.

When you output a Date by calling toString() (which is what System.out.println("Data type is Date = " + gmt); does) you will get that Date according to the system time zone, because that is what Date.toString() returns.
Converts this Date object to a String of the form:
dow mon dd hh:mm:ss zzz yyyy
where:
...
zzz is the time zone (and may reflect daylight saving time). Standard time
zone abbreviations include those recognized by the method parse. If time
zone information is not available, then zzz is empty - that is, it
consists of no characters at all.
So, to get the output you expect use your dateFormatter to format it again.
String gmtS = dateFormatter.format(initial);
Date gmt = dateFormatter.parse(gmtS);
System.out.println("Data type is Date = " + dateFormatter.format(gmt));

tl;dr
Instant.now().toString()
2019-02-07T19:15:29.123456Z
Avoid legacy date-time classes
You are using date-time classes that are terribly troublesome, with many flaws in design.
First, you should know that java.util.Date represents a moment in UTC, always in UTC by definition. But its toString method tells a lie, dynamically applying the JVM’s current default time zone while generating the text representing the moment in the Date object.
java.time
The modern approach uses the java.time classes.
Instant
For a moment in UTC, use Instant. Like java.time.Date it represents a moment always in UTC (but with a finer resolution of nanoseconds versus milliseconds). Indeed, you can convert easily back-and-forth between Date and Instant by using new methods added to the old class.
Unlike toString on Date, the toString method on Instant always tells the truth. The method generates text in standard ISO 8601 format. The T in the middle separates the date portion from the time portion. The Z on the end is short for UTC and is pronounced “Zulu”.
Instant.now().toString(): 2019-01-23T12:34:56.123456789Z
OffsetDateTime
The Instant class is a basic building-block class in java.time, with limited functionality. If you want more flexible formatting, use the OffsetDateTime class with the offset set to UTC.
OffsetDateTime odt = instant.atOffset( ZoneOffset.UTC ) ;
Or skip the Instant class.
OffsetDateTime odt = OffsetDateTime.now( ZoneOffset.UTC ) ;
To generate text representing the value of the OffsetDateTime object, use the DateTimeFormatter class. Search Stack Overflow as this has been covered many many times already.
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, Java SE 11, and later - 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
Most 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.