import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        System.out.println(ZonedDateTime.parse("2018-05-23T23:18:31.000Z")
                .format(DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss", Locale.ENGLISH)));
    }
}