java - ZonedDateTime.now() causes org.threeten.bp.zone.ZoneRulesException

I just found this library to use java.time from Java 8 on Android. In my TimePickerDialog I ask for a time, and after that I have to send a HTTP request to a server with a Date object in it (with the time from the dialog), in this format: "YYYY-MM-DDTHH:MM:SS+HH:MM"
I started trying with the usual classes (Calendar, Date, SimpleDateFormat), but after a while I gave up and looked for a cleaner solution and found the ZonedDateTime class from Java 8. It looks like exactly the class I want to use, but when I try to create an instance of it with ZonedDateTime.now(), I get the following stacktrace:

org.threeten.bp.zone.ZoneRulesException: No time-zone data files registered
  at org.threeten.bp.zone.ZoneRulesProvider.getProvider(ZoneRulesProvider.java:176)
  at org.threeten.bp.zone.ZoneRulesProvider.getRules(ZoneRulesProvider.java:133)

  at org.threeten.bp.ZoneRegion.ofId(ZoneRegion.java:143)
  at org.threeten.bp.ZoneId.of(ZoneId.java:357)
  at org.threeten.bp.ZoneId.of(ZoneId.java:285)
  at org.threeten.bp.ZoneId.systemDefault(ZoneId.java:244)
  at org.threeten.bp.Clock.systemDefaultZone(Clock.java:137)
  at org.threeten.bp.ZonedDateTime.now(ZonedDateTime.java:168)
  at eu.arrowhead.arrowheaddemo.ReservationsActivity.onTimeSet(ReservationsActivity.java:162)
  at eu.arrowhead.arrowheaddemo.TimePickerFragment.onTimeSet(TimePickerFragment.java:56)
  at android.app.TimePickerDialog.onClick(TimePickerDialog.java:141)
  at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:164)

  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:154)
  at android.app.ActivityThread.main(ActivityThread.java:6077)
  at java.lang.reflect.Method.invoke(Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

I did AndroidThreeTen.init(this); as per the documantion in my application class (in onCreate), so I dont know what causes the problem.

Bonus question: once I got it working and I have the date I want to send in the ZonedDateTime object, how do I convert it to a simple java.util.Date ? Thank you very much in advance.

EDIT: proof for the init:

public class MyApplication extends Application{

    @Override
    public void onCreate() {
        super.onCreate();
        AndroidThreeTen.init(this);

    }
}

Btw API level is 24.