TerminService.java

package service;

import org.joda.time.DateTime;
import org.joda.time.DateTimeFieldType;

public class TerminService {

  public static DateTime nextTermin(DateTime d){
    int hour = d.get(DateTimeFieldType.hourOfDay());
    int hoursToNextTermin = 3 - (hour % 3);
    DateTime nextTermin = d
        .withMillisOfSecond(0)
        .withSecondOfMinute(0)
        .withMinuteOfHour(0)
        .plusHours(hoursToNextTermin);  // 0,3,6,9,12,15,18,21
    return nextTermin;
  }

  public static DateTime tomorrowAtMidnight(DateTime d){
    return d.plusDays(1).withTimeAtStartOfDay();
  }

 }