Format a Date String with Time zone and return Date object

Question

I need to format a string date with given time zone and return the date object back. I am currently in IST time zone.

So IST is 5 hours and 30 minutes ahead of UTC.

public void getDate(){
  String dateStr = "11/25/2016T13:30:00.000";
  String dateFormat = "MM/dd/yyyy'T'HH:mm:ss.SSS";
  Date date = formatedStringToDate(dateStr, dateFormat);
  System.out.println(date);
}

public static Date formatedStringToDate(final String date, final String dateFormat) throws ParseException {
        final SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
        Date parsedDate = null;
        if (date != null) {
            try {
                parsedDate = sdf.parse(date);
            } catch (ParseException e) {
                throw e;
            }
        }
        return parsedDate;
}

I get the below out put.

Fri Nov 25 19:00:00 **IST** 2016

The time seems to be change from 5.30 hours but then if its a IST to UCT time converstion, it should be 5.30 hours before 13:30:00 which is 08:00:00?

Also how could I change the highlighted IST part of out put string to show the currect time zone in this case UTC?

Answer 1

When you call toString on a Date (by printing it) you get the default format (because a Date is an object that stores a number of milliseconds, or nanoseconds in Java 9+, since an epoch). To see the result in UTC you need something like,

final DateFormat sdf = DateFormat.getDateTimeInstance(DateFormat.FULL,
        DateFormat.FULL);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
Date date = formatedStringToDate(dateStr, dateFormat);
System.out.println(sdf.format(date)); // <-- format the Date

Answer 2

tl;dr

LocalDateTime.parse( "2017-11-25T13:30:00.000" )
    .atZone( ZoneId.of( "Asia/Kolkata" ) )

2017-11-25T13:30+05:30[Asia/Kolkata]

java.time

The modern approach uses the java.time classes that replaced the troublesome old legacy date-time classes.

Parse your input string as a LocalDateTime given the lack of any indicator of zone or offset-from-UTC.

Using standard ISO 8601 format for such strings is preferred. The java.time classes use the standard formats by default when parsing/generating strings.

LocalDateTime ldt = LocalDateTime.parse( "2017-11-25T13:30:00.000" ) ;

ldt.toString(): 2017-11-25T13:30

If you are certain this date-time was intended to represent a moment by the wall-clock time of India, then assign a time zone to produce a ZonedDateTime object.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "Asia/Kolkata" ) ;
ZonedDateTime zdt = ldt.atZone( z ) ;

zdt.toString(): 2017-11-25T13:30+05:30[Asia/Kolkata]

You can adjust into another zone for comparison.

ZonedDateTime zdtMontreal = zdt.withZoneSameInstant( ZoneId.of( "America/Montreal") );

zdtMontreal.toString(): 2017-11-25T03:00-05:00[America/Montreal]

To parse/generate strings in other formats such as the one in your Question, use the DateTimeFormatter or DateTimeFormatterBuilder classes. Search Stack Overflow for more info, as these have been covered extensively.

DateTimeFormatter f = DateTimeFormatter.ofPattern( "MM/dd/uuuu'T'HH:mm:ss.SSS" , Locale.US ) ;

Use that formatter for parsing.

LocalDateTime ldt = LocalDateTime.parse( "11/25/2016T13:30:00.000" , f ) ;

And for generating.

String output = ldt.format( f ) ;  // Generate string.

Consider using ISO 8601 formats instead.

---

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.

With a JDBC driver complying with JDBC 4.2 or later, you may exchange java.time objects directly with your database. No need for strings or 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.