Parsing Java String into GMT Date

Question

I'm trying to parse a String that represents a date using GMT, but it prints out in my timezone on my PC (pacific). When I run the below I get the below output. Any ideas on how to get the parse to parse and return a GMT date? If you look below I'm setting the timezone using format.setTimeZone(TimeZone.getTimeZone("GMT")); but its not producing the desired result.

output from below code:

Mon Oct 29 05:57:00 PDT 2012

 package javaapplication1;

    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.TimeZone;


    public class JavaApplication1 {

        public static void main(String[] args) throws ParseException {
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");
            format.setTimeZone(TimeZone.getTimeZone("GMT"));
            System.out.println(format.parse("2012-10-29T12:57:00-0000"));
        }
    }

`-0000` does not necessarily denote GMT. It’s not completely clear what it does denote or whether it’s allowed (according to [the ISO 8601 standard](https://en.wikipedia.org/wiki/ISO_8601)) at all. It may mean an undefined offset from UTC. GMT would be denoted either by `Z` or by `+0000` with a plus sign. — Ole V.V., Nov 04 '21 at 09:47
For new readers to this question I recommend you don’t use `SimpleDateFormat` and `Date`. Those classes are poorly designed and long outdated, the former in particular notoriously troublesome. Instead use `OffsetDateTime` and `DateTimeFormatter`, both from [java.time, the modern Java date and time API](https://docs.oracle.com/javase/tutorial/datetime/). — Ole V.V., Nov 04 '21 at 10:14

Yogendra Singh · Accepted Answer · 2012-10-31T20:31:34.710

You are using format.setTimeZone(TimeZone.getTimeZone("GMT")); in the formatter, which is being used in formatting the string into date i.e.

      Date date = format.parse("2012-10-29T12:57:00-0000");

is parsed treating 2012-10-29T12:57:00-0000 was a GMT value, but you are printing date which uses local timezome in printing hence you are noticing the difference.

If you want to print the date back in GMT, please use:

    String formattedDate = format.format(date);

and print the formattedDate. This will be GMT.

    System.out.println(formattedDate);

score 0 · Answer 2 · 2012-10-31T20:32:23.807

Complete working example

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

public class Main
{
    public static void main(String[] args)
    {
        final SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy hh:mm:ss z", Locale.ENGLISH);
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
        System.out.println(sdf.format(new Date())); 
        // ^^^ note printing the results of sdf.format() 
        //     not a raw `Date`
    }
}

result : 31-10-2012 08:32:01 UTC Note what I am actually printing out!

score 0 · Answer 3 · answered Oct 31 '12 at 20:14

System.out.println(format.parse("2012-10-29T12:57:00-0000"));

Parses the date as GMT and returns a Date object. Then it prints it out (using the default toString()-method). This just uses the settings of your computer. so you should use:

Date parsedDate=format.parse("2012-10-29T12:57:00-0000");
System.out.println(format.format(parsedDate));

score 0 · Answer 4 · answered Sep 25 '15 at 16:24

Try this,

public static String converterGMTToLocal(String datahora_gmt)
{
    try {
        SimpleDateFormat fmt = new SimpleDateFormat("YYYY-MM-dd HH:mm");
        Calendar cal = Calendar.getInstance();
        cal.setTime(fmt.parse(datahora_gmt));
        cal.add(Calendar.HOUR, -3);

        return fmt.format(cal.getTime());

    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        return e.getMessage();
    }
}

Change the values for your project...make the appropriate changes

score 0 · Answer 5 · answered Nov 04 '21 at 10:12

java.time

I recommend that you use java.time, the modern Java date and time API, for your date and time work. I prefer using the following formatter for parsing.

private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()
        .append(DateTimeFormatter.ISO_LOCAL_DATE_TIME)
        .appendPattern("xx")
        .toFormatter(Locale.ROOT);

Parse into an OffsetDateTime in order to preserve the offset from the string (-0000).

    String gmtString = "2012-10-29T12:57:00-0000";
    OffsetDateTime gmtDateTime = OffsetDateTime.parse(gmtString, PARSER);
    System.out.println(gmtDateTime);

Output is:

2012-10-29T12:57Z

The trailing Z in the output denotes UTC or offset 0 from UTC, which for our purpose we can regard as equivalent to GMT. If we prefer, we can also format back using the same (or a different) formatter before printing:

    System.out.println(gmtDateTime.format(PARSER));

2012-10-29T12:57:00+0000

In this case you will probably want to name the formatter something else than PARSER.

Offset -0000 is not legal

I wonder where you got that string because it adheres to the standard ISO 8601 format except ISO 8601 does not permit -0000 as an offset. Offset zero must be given as Z, +00:00, +0000 or +00. Fortunately for us Java is lenient on this point and accepts -0000 as equivalent to +0000.

Links

Oracle tutorial: Date Time explaining how to use java.time.
Question: What is the difference between UTC and GMT?
Wikipedia article: ISO 8601

Parsing Java String into GMT Date

5 Answers5

Complete working example

java.time

Offset -0000 is not legal

Links

Linked

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