diff --git a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/business/CalendarTaskRefresher.java b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/business/CalendarTaskRefresher.java
index afd4924..ccef4a3 100644
--- a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/business/CalendarTaskRefresher.java
+++ b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/business/CalendarTaskRefresher.java
@@ -2,9 +2,12 @@ package de.kreth.vaadin.clubhelper.vaadinclubhelper.business;
 
 import java.util.List;
 
+import javax.validation.ConstraintViolationException;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.dao.DataIntegrityViolationException;
 import org.springframework.scheduling.annotation.Scheduled;
 import org.springframework.stereotype.Component;
 
@@ -27,8 +30,18 @@ public class CalendarTaskRefresher {
 	public void synchronizeCalendarTasks() {
 		List<ClubEvent> events = business.loadEvents(null, true);
 		for (ClubEvent e : events) {
-			log.trace("try storing {}", e);
-			dao.save(e);
+			if (dao.get(e.getId()) != null) {
+				try {
+					log.trace("try inserting {}", e);
+					dao.save(e);
+				} catch (ConstraintViolationException | DataIntegrityViolationException ex) {
+					log.warn("Insert failed, updating {}", e);
+					dao.update(e);
+				}
+			} else {
+				log.trace("try updating {}", e);
+				dao.update(e);
+			}
 			log.debug("successfully stored {}", e);
 		}
 	}
diff --git a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/AbstractDaoImpl.java b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/AbstractDaoImpl.java
index 99a4a57..3a9df70 100644
--- a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/AbstractDaoImpl.java
+++ b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/AbstractDaoImpl.java
@@ -11,7 +11,7 @@ import org.springframework.transaction.annotation.Transactional;
 public abstract class AbstractDaoImpl<T> implements IDao<T> {
 
 	@Autowired
-	EntityManager em;
+	protected EntityManager em;
 
 	private final Class<T> entityClass;
 
@@ -23,16 +23,20 @@ public abstract class AbstractDaoImpl<T> implements IDao<T> {
 	@Override
 	@Transactional
 	public void save(T obj) {
-		// EntityTransaction tx = em.getTransaction();
-		// tx.begin();
-		// try {
 		em.persist(obj);
-		// tx.commit();
-		// } catch (Exception e) {
-		// tx.rollback();
-		// }
 	}
 
+	@Override
+	@Transactional
+	public T update(T obj) {
+		return em.merge(obj);
+	}
+	
+	@Override
+	public T get(Object primaryKey) {
+		return em.find(entityClass, primaryKey);
+	}
+	
 	@Override
 	public List<T> list() {
 
diff --git a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/IDao.java b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/IDao.java
index b485d3f..beadcaa 100644
--- a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/IDao.java
+++ b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/dao/IDao.java
@@ -5,5 +5,7 @@ import java.util.List;
 public interface IDao<T> {
 
 	void save(T obj);
+	T update(T obj);
 	List<T> list();
+	T get(Object primaryKey);
 }