I'm trying to parse the date returned as a value from the HTML5 datetime
input field. Try it in Opera to see an example. The date returned looks like this: 2011-05-03T11:58:01Z
.
I'd like to parse that into a Java Date or Calendar Object.
Ideally a solution should have the following things:
Instant.parse( "2011-05-03T11:58:01Z" )
Actually, RFC 3339 is but a mere self-proclaimed “profile” of the actual standard, ISO 8601.
The RFC is different in that it purposely violates ISO 8601 to allow a negative offset of zero hours (-00:00
) and gives that a semantic meaning of “offset unknown“. That semantic seems like a very bad idea to me. I advise sticking with the more sensible ISO 8601 rules. In ISO 8601, having no offset at all means the offset is unknown – an obvious meaning, whereas the RFC rule is abstruse.
The modern java.time classes use the ISO 8601 formats by default when parsing/generating strings.
Your input string represents a moment in UTC. The Z
on the end is short for Zulu
and means UTC.
Instant
(not Date
)The modern class Instant
represents a moment in UTC. This class replaces java.util.Date
, and uses a finer resolution of nanoseconds rather than milliseconds.
Instant instant = Instant.parse( "2011-05-03T11:58:01Z" ) ;
ZonedDateTime
(not Calendar
)To see that same moment through the wall-clock time used by the people of a certain region (a time zone), apply a ZoneId
to get a ZonedDateTime
. This class ZonedDateTime
replaces the java.util.Calendar
class.
ZoneId z = ZoneId.of( "Africa/Tunis" ) ;
ZonedDateTime zdt = instant.atZone( z ) ; // Same moment, same point on the timeline, different wall-clock time.
I strongly recommend avoiding the legacy date-time classes when possible. But if you must inter-operate with old code not yet updated to java.time, you may convert back-and-forth. Call new methods added to the old classes.
Instant
replaces java.util.Date
.
java.util.Date myJUDate = java.util.Date.from( instant ) ; // From modern to legacy.
Instant instant = myJUDate.toInstant() ; // From legacy to modern.
ZonedDateTime
replaces GregorianCalendar
.
java.util.GregorianCalendar myGregCal = java.util.GregorianCalendar.from( zdt ) ; // From modern to legacy.
ZonedDateTime zdt = myGregCal.toZonedDateTime() ; // From legacy to modern.
If you have a java.util.Calendar
that is actually a GregorianCalendar
, cast.
java.util.GregorianCalendar myGregCal = ( java.util.GregorianCalendar ) myCal ; // Cast to the concrete class.
ZonedDateTime zdt = myGregCal.toZonedDateTime() ; // From legacy to modern.
Regarding your Question’s specific issues…
The java.time classes are built into Java 8, 9, 10, and later. An implementation is also included in later Android. For earlier Java and earlier Android, see the next section of this Answer.
The various java.time classes handle every ISO 8601 format I know of. They even handle some formats that mysteriously disappeared from later editions of the standard.
For other formats, see the parse
and toString
methods of the various classes such as LocalDate
, OffsetDateTime
, and so on. Also, search Stack Overflow as there are many examples and discussions on this topic.
To validate input strings, trap for DateTimeParseException
.
try {
Instant instant = Instant.parse( "2011-05-03T11:58:01Z" ) ;
} catch ( DateTimeParseException e ) {
… handle invalid input
}
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?
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.