Welcome to in Ireland, the only country where the clock is turned _back_ for daylight saving time.

output.txt

--- Joda Time ---
Winter:
Monday, 1 January 2018 12:00:00 AM GMT
Is standard offset? true
Summer:
Sunday, 1 July 2018 1:00:00 AM IST
Is standard offset? false
--- ICU ---
Winter:
Monday, 1 January 2018 at 12:00:00 am Greenwich Mean Time
Is standard offset? false
Summer:
Sunday, 1 July 2018 at 1:00:00 am Irish Standard Time
Is standard offset? true

TestIreland.java

import java.util.Locale;

import com.ibm.icu.text.DateFormat;
import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.TimeZone;
import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;
import org.junit.Test;

public class TestIreland
{
    @Test
    public void testIrelandJoda()
    {
        System.out.println("--- Joda Time ---");

        DateTimeZone zone = DateTimeZone.forID("Europe/Dublin");
        DateTimeFormatter dateTimeFormatter = DateTimeFormat.fullDateTime().withZone(zone);

        System.out.println("Winter:");
        DateTime dateTime1 = new DateTime(2018, 1, 1, 0, 0, 0, DateTimeZone.UTC).withZone(zone);
        System.out.println(dateTimeFormatter.print(dateTime1));
        System.out.println("Is standard offset? " + zone.isStandardOffset(dateTime1.getMillis()));

        System.out.println("Summer:");
        DateTime dateTime2 = new DateTime(2018, 7, 1, 0, 0, 0, DateTimeZone.UTC).withZone(zone);
        System.out.println(dateTimeFormatter.print(dateTime2));
        System.out.println("Is standard offset? " + zone.isStandardOffset(dateTime2.getMillis()));
    }

    @Test
    public void testIrelandIcu()
    {
        System.out.println("--- ICU ---");

        TimeZone zone = TimeZone.getTimeZone("Europe/Dublin");
        Locale locale = new Locale("en", "IE");
        DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL);
        dateFormat.setTimeZone(zone);
        Calendar calendar = Calendar.getInstance(zone, locale);

        System.out.println("Winter:");
        calendar.setTimeInMillis(new DateTime(2018, 1, 1, 0, 0, 0, DateTimeZone.UTC).getMillis());
        System.out.println(dateFormat.format(calendar.getTime()));
        System.out.println("Is standard offset? " + zone.inDaylightTime(calendar.getTime()));

        System.out.println("Summer:");
        calendar.setTimeInMillis(new DateTime(2018, 7, 1, 0, 0, 0, DateTimeZone.UTC).getMillis());
        System.out.println(dateFormat.format(calendar.getTime()));
        System.out.println("Is standard offset? " + zone.inDaylightTime(calendar.getTime()));
    }
}