Format Date in Java using ISO8601 including timezone

To format a java.util.Date as an ISO8601 timestamp including the correct timezone, java.time.OffsetDateTime can be used.

package de.lhorn.playground;

import java.time.Instant;
import java.time.OffsetDateTime;
import java.time.ZoneOffset;
import java.util.Date;
import java.util.TimeZone;

public class FormatDatetimeExample {

        public static void main(String[] args) {
                // The Date we want to format.
                Date date = new Date();
                long millis = date.getTime();

                // The local timezone of the system we run this code on.
                TimeZone timeZone = TimeZone.getDefault();

                // We calculate the timezone offset that applies to the given Date.
                int offset = timeZone.getOffset(millis);
                ZoneOffset zoneOffset = ZoneOffset.ofTotalSeconds(offset / 1_000);

                // Convert the Date into an OffsetDateTime using the calculated ZoneOffset.
                Instant instant = date.toInstant();
                OffsetDateTime odt = instant.atOffset(zoneOffset);

                // The output is something like "2019-10-30T08:16:39.535+01:00" which
                // includes the correct timezone in which I am currently located (Europe/Berlin).
                System.out.println("odt: " + odt.toString());