Not able to parse date

Question

I am stuck trying to parse this date string, can any one please help, getting the below error while parsing

Exception in thread "main" java.text.ParseException: Unparseable date: "2022-09-22T11:22:39GMT-06:00" at java.base/java.text.DateFormat.parse(DateFormat.java:396) at Main.main(Main.java:16)

import java.text.SimpleDateFormat;
import java.time.Instant;
import java.time.LocalDate;
import java.time.OffsetDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.TimeZone;
import java.text.ParseException;

public class Main {
   public static void main(String[] args) throws ParseException {
   String dateString = "2022-09-22T11:22:39GMT-06:00";
   System.out.println("Hello World!");
   SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd     hh:mm:ss a");
   simpleDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
   simpleDateFormat.parse(dateString);
  }
}

Can any one help this parse, not able to parse this string

Basil Bourque · Answer

tl;dr

Use java.time. Never use the legacy date-time classes SimpleDateFormat, Date, Calendar, etc.

OffsetDateTime
.parse( "2022-09-22T11:22:39GMT-06:00".replace( "GMT" , "" ) ) 
.withOffsetSameInstant( ZoneOffset.UTC ) 
.format(
    DateTimeFormatter
    .ofLocalizedDateTime( … )
    .withLocale( … )
)

ISO 8601

The ideal solution would include educating the publisher of your date about the ISO 8601 standard for communicating date-time values as text.

Your input text nearly complies with ISO 8601. The GMT part is redundant as we know -06:00 means “six hours behind UTC/GMT”.

To comply with ISO 8601, delete that GMT text.

String inputIso8601 = input.replace( "GMT" , "" ) ;

java.time

You are using terrible date-time classes that were years ago supplanted by the modern java.time classes defined in JSR 310. Oracle Corp provides a tutorial on java.time at no cost.

`OffsetDateTime`

Your input represents a date and time as seen with a particular offset from UTC. So parse as a OffsetDateTime object.

OffsetDateTime odt = OffsetDateTime.parse( inputIso8601 ) ;

Adjust to UTC

Apparently you want to adjust that to be the same moment but as seen with an offset of zero hours-minutes-seconds from UTC.

We have a constant for zero offset: ZoneOffset.UTC.

OffsetDateTime odtInUtc = odt.withOffsetSameInstant( ZoneOffset.UTC ) ;

Generate text

Next you want to generate some text to represent the value of our odtInUtc object. You can do that in either of two ways. I recommend the first.

Automatically localize. Use DateTimeFormatter.ofLocalizedDateTime.
Define a hard-coded formatting pattern with DateTimeFormatter.ofPattern.

Both of these have been covered many times already on Stack Overflow. Search to learn more.

Tal Glik · Answer

If you set the GMT in the setTimeZone command why do you need the GMT in the dateString?

Instead of: SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss a");

Try this: SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ss");