ZonedDateTime correctly parses "GMT" zone from pattern 'O' but not "UTC"

Question

The following correctly parses the text input "2022-12-29 01:16:03 GMT+08:00".

public ZonedDateTime parseZonedDateTime(String timeStr) {
  DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss O");

  ZonedDateTime zonedDateTime = ZonedDateTime.parse(timeStr, dtf);

  return zonedDateTime;
}

However, if the input string is "2022-12-29 01:16:03 UTC-08:00", ZonedDateTime.parse() method throws

java.time.format.DateTimeParseException: Text '2022-12-29 01:16:03 UTC-08:00' could not be parsed at index 20

See this code run on Java 12 at Ideone.com.

According to the DateTimeFormatter doc, https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html

both "GMT+08:00" and "UTC-08:00" are considered localized zone-offset 'O'.

What should be the correct pattern so that the parser accepts both GMT and UTC inputs?

I have tried using the format "yyyy-MM-dd HH:mm:ss OOOO" but the behavior is the same.

There is a similar question Why does `GMT+8` fail to parse with pattern `O` despite being copied straight out of doc? and according to this, the bug was fixed in Java 9 build b116.

However I'm using java 17.0.4.1-librca

Answer 1

What should be the correct pattern so that the parser accepts both GMT and UTC inputs?

Use V instead of O i.e. use the pattern, yyyy-MM-dd HH:mm:ss VV.

Demo:

public class Main {
    public static void main(String args[]) {
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss VV", Locale.ENGLISH);
        Stream.of(
                "2022-12-29 01:16:03 GMT+08:00",
                "2022-12-29 01:16:03 UTC-08:00"
            )
            .map(s -> ZonedDateTime.parse(s, dtf))
            .forEach(System.out::println);
        ;
    }
}

Output:

2022-12-29T01:16:03+08:00[GMT+08:00]
2022-12-29T01:16:03-08:00[UTC-08:00]

Online Demo

Learn more about the modern Date-Time API from Trail: Date Time.