How to obtain UTC format with +0000 in Java?

Question

I want to change the date format from "20230523154325" to 2023-05-23T15:43:25+0000".
And I have this piece of code, but unfortunately the result is this: "2023-05-23T15:43:25+0300".
So I don't want to have +0300, I want to have +0000 at the end. So, it should be exactly the same for this part 2023-05-23T15:43:25, but instead of +0300 should be +0000. It's important to have this +0000 at the end. Any feedback will be appreciated!

public static void main(String[] args) {
    String oldDate = "20230523154325";
    SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
    Date newDateFormat = null;

    try {
        newDateFormat = sdf.parse(oldDate);
    } catch (ParseException e) {
        throw new RuntimeException(e);
    }
    
    SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");
    System.out.println("The date is " + sdf1.format(newDateFormat));
}

Answer 1

I want to change the date format from 20230523154325 to 2023-05-23T15:43:25+0000

You can do that with java.time if you are using Java 8 or higher.

Example Code

public static void main(String[] args) {
    // example input
    String oldDate = "20230523154325";
    // prepare a parser
    DateTimeFormatter parser = DateTimeFormatter.ofPattern("uuuuMMddHHmmss");
    // parse the oldDate with the parser
    LocalDateTime ldt = LocalDateTime.parse(oldDate, parser);
    // print the result (NO OFFSET SO FAR!!!)
    System.out.println(ldt);
    // add an offset (UTC = +00:00 = Z)
    OffsetDateTime odt = ldt.atOffset(ZoneOffset.UTC);
    // print it
    System.out.println(odt);
    // prepare a formatter for the desired output
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ssxxxx");
    // then print the datetime plus offset in the desired format
    System.out.println(odt.format(formatter));
}

Output

2023-05-23T15:43:25
2023-05-23T15:43:25Z
2023-05-23T15:43:25+0000

There are prebuilt ones for standard/common formats like DateTimeFormatter.ISO_OFFSET_DATE_TIME, which are worth a look. However, you have to create those two DateTimeFormatters manually in this case, because none of the prebuilt ones can parse your input format and none of them can produce your desired output.

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Why did your attempt fail to produce the desired result?

Your attempt involves the zone/offset of your machine/jvm, which will even change the offset when the code is executed on another machine with a different zone/offset.

That's why you

• should stop using java.util.Date and java.text.SimpleDateFormat whenever/wherever you can…
• should switch to java.time because you have full control over zone/offset handling

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Compact / Short Version

public static void main(String[] args) {
    String oldDate = "20230523154325";
    DateTimeFormatter parser = DateTimeFormatter.ofPattern("uuuuMMddHHmmss");
    DateTimeFormatter formatter = DateTimeFormatter
                                    .ofPattern("uuuu-MM-dd'T'HH:mm:ssxxxx");
    String desiredResult = LocalDateTime.parse(oldDate, parser)
                                        .atOffset(ZoneOffset.UTC)
                                        .format(formatter);
    System.out.println(desiredResult);
}

Output

2023-05-23T15:43:25+0000