diff --git a/src/se/hal/daemon/SensorDataAggregatorDaemon.java b/src/se/hal/daemon/SensorDataAggregatorDaemon.java
index 554df8f1..8fe1c1d0 100755
--- a/src/se/hal/daemon/SensorDataAggregatorDaemon.java
+++ b/src/se/hal/daemon/SensorDataAggregatorDaemon.java
@@ -89,38 +89,42 @@ public class SensorDataAggregatorDaemon implements HalDaemon {
     	long sensorId = sensor.getId();
     	AggregationMethod aggrMethod = sensor.getDeviceConfig().getAggregationMethod();
     	DBConnection db = HalContext.getDB();
-    	PreparedStatement stmt = null;
+    	PreparedStatement stmt;
     	try {
-    		Long maxAggrTimestampInDB = getLatestAggrTimestamp(db, sensor, aggrPeriodLength);
-    		if(maxAggrTimestampInDB == null)
-    			maxAggrTimestampInDB = 0l;
-    		
-    		long latestCompletePeriodEndTimestamp = new UTCTimePeriod(aggregationStartTime, aggrPeriodLength).getPreviosPeriod().getEndTimestamp();
-    		long oldestPeriodStartTimestamp = new UTCTimePeriod(aggregationStartTime-ageLimitInMs, aggrPeriodLength).getStartTimestamp();
+    	    // DB timestamps
+            long dbMaxRawTimestamp = getLatestRawTimestamp(db, sensor);
+    		long dbMaxAggrEndTimestamp = getLatestAggrEndTimestamp(db, sensor, aggrPeriodLength);
+    		// Periods
+    		long periodLatestEndTimestamp = new UTCTimePeriod(aggregationStartTime, aggrPeriodLength).getPreviosPeriod().getEndTimestamp();
+    		long periodOldestStartTimestamp = new UTCTimePeriod(aggregationStartTime-ageLimitInMs, aggrPeriodLength).getStartTimestamp();
 
             // Check if the sensor has stopped responding for 15 min or 3 times the data interval and alert the user
             if (aggrPeriodLength == AggregationPeriodLength.FIVE_MINUTES) {
-                Long maxRawTimestampInDB = getLatestRawTimestamp(db, sensor);
                 long dataInterval = sensor.getDeviceConfig().getDataInterval();
                 if (dataInterval < UTCTimeUtility.FIVE_MINUTES_IN_MS)
                     dataInterval = UTCTimeUtility.FIVE_MINUTES_IN_MS;
-                if (maxRawTimestampInDB != null &&
-                        maxRawTimestampInDB + (dataInterval * 3) < System.currentTimeMillis()) {
-                    logger.fine("Sensor \"" + sensorId + "\" has stopped sending data");
+                if (dbMaxRawTimestamp > 0 &&
+                        dbMaxRawTimestamp + (dataInterval * 3) < System.currentTimeMillis()) {
+                    logger.fine("Sensor \"" + sensorId + "\" stopped sending data at: "+ dbMaxRawTimestamp);
                     HalAlertManager.getInstance().addAlert(new HalAlert(AlertLevel.WARNING,
-                            "Sensor \"" + sensor.getName() + "\" has stopped responding",
-							"since <span class=\"timestamp\">"+maxRawTimestampInDB+"</span>",
+                            "Sensor \"" + sensor.getName() + "\" stopped responding",
+							"at <span class=\"timestamp\">"+dbMaxRawTimestamp+"</span>",
 							AlertTTL.DISMISSED));
                 }
             }
 
-    		if(latestCompletePeriodEndTimestamp == maxAggrTimestampInDB){
-    			logger.fine("no new data to evaluate - aggregation is up to date");
+            // Is there any new data to evaluate?
+    		if(dbMaxRawTimestamp < dbMaxAggrEndTimestamp || dbMaxRawTimestamp < periodOldestStartTimestamp){
+    			logger.fine("No new data to evaluate - aggregation is up to date");
     			return;
-    		}else{
-    			logger.fine("evaluating period: "+ (maxAggrTimestampInDB+1) + "=>" + latestCompletePeriodEndTimestamp + " (" + UTCTimeUtility.getDateString(maxAggrTimestampInDB+1) + "=>" + UTCTimeUtility.getDateString(latestCompletePeriodEndTimestamp) + ") with expected sample count: " + expectedSampleCount);
     		}
-    		
+
+    		// Start processing
+			logger.fine("evaluating period: "+
+					(dbMaxAggrEndTimestamp+1) + "=>" + periodLatestEndTimestamp +
+					" (" + UTCTimeUtility.getDateString(dbMaxAggrEndTimestamp+1) + "=>" +
+					UTCTimeUtility.getDateString(periodLatestEndTimestamp) + ") " +
+					"with expected sample count: " + expectedSampleCount);
     		stmt = db.getPreparedStatement("SELECT *, 1 AS confidence FROM sensor_data_raw"
     				+" WHERE sensor_id == ?"
     					+ " AND timestamp > ?"
@@ -128,16 +132,16 @@ public class SensorDataAggregatorDaemon implements HalDaemon {
     					+ " AND timestamp >= ? "
     				+" ORDER BY timestamp ASC");
     		stmt.setLong(1, sensorId);
-    		stmt.setLong(2, maxAggrTimestampInDB);
-    		stmt.setLong(3, latestCompletePeriodEndTimestamp);
-    		stmt.setLong(4, oldestPeriodStartTimestamp);
+    		stmt.setLong(2, dbMaxAggrEndTimestamp);
+    		stmt.setLong(3, periodLatestEndTimestamp);
+    		stmt.setLong(4, periodOldestStartTimestamp);
     		DBConnection.exec(stmt, new DataAggregator(sensorId, aggrPeriodLength, expectedSampleCount, aggrMethod, aggregationStartTime));
     	} catch (SQLException e) {
             logger.log(Level.SEVERE, null, e);
 		}
     }
 
-    private Long getLatestAggrTimestamp(DBConnection db, Sensor sensor, AggregationPeriodLength aggrPeriodLength) throws SQLException {
+    private long getLatestAggrEndTimestamp(DBConnection db, Sensor sensor, AggregationPeriodLength aggrPeriodLength) throws SQLException {
         PreparedStatement stmt = db.getPreparedStatement("SELECT MAX(timestamp_end) FROM sensor_data_aggr"
                 + " WHERE sensor_id == ?"
                 + " AND timestamp_end-timestamp_start == ?");
@@ -153,12 +157,15 @@ public class SensorDataAggregatorDaemon implements HalDaemon {
             default:
                 throw new IllegalArgumentException("aggregation period length is not supported.");
         }
-        return DBConnection.exec(stmt, new SimpleSQLResult<Long>());
+        Long timestamp = DBConnection.exec(stmt, new SimpleSQLResult<Long>());
+        return (timestamp == null ? 0l : timestamp);
     }
-    private Long getLatestRawTimestamp(DBConnection db, Sensor sensor) throws SQLException {
-        PreparedStatement stmt = db.getPreparedStatement("SELECT MAX(timestamp) FROM sensor_data_raw WHERE sensor_id == ?");
+    private long getLatestRawTimestamp(DBConnection db, Sensor sensor) throws SQLException {
+        PreparedStatement stmt = db.getPreparedStatement(
+                "SELECT MAX(timestamp) FROM sensor_data_raw WHERE sensor_id == ?");
         stmt.setLong(1, sensor.getId());
-        return DBConnection.exec(stmt, new SimpleSQLResult<Long>());
+        Long timestamp = DBConnection.exec(stmt, new SimpleSQLResult<Long>());
+        return (timestamp == null ? 0l : timestamp);
     }
 
 
@@ -191,10 +198,13 @@ public class SensorDataAggregatorDaemon implements HalDaemon {
 				int samples = 0;
 				long highestSequenceId = Sensor.getHighestSequenceId(sensorId);
 				PreparedStatement preparedInsertStmt = HalContext.getDB().getPreparedStatement(
-						"INSERT INTO sensor_data_aggr(sensor_id, sequence_id, timestamp_start, timestamp_end, data, confidence) VALUES(?, ?, ?, ?, ?, ?)");
+						"INSERT INTO sensor_data_aggr" +
+                                "(sensor_id, sequence_id, timestamp_start, timestamp_end, data, confidence) " +
+                                "VALUES(?, ?, ?, ?, ?, ?)");
 				while(result.next()){
 					if(sensorId != result.getInt("sensor_id")){
-						throw new IllegalArgumentException("found entry for aggregation for the wrong sensorId (expecting: "+sensorId+", but was: "+result.getInt("sensor_id")+")");
+						throw new IllegalArgumentException("found entry for aggregation for the wrong sensorId " +
+                                "(expecting: "+sensorId+", but was: "+result.getInt("sensor_id")+")");
 					}
 					
 					long timestamp = result.getLong("timestamp");
@@ -218,7 +228,8 @@ public class SensorDataAggregatorDaemon implements HalDaemon {
 				}
 				
 				//check if the last period is complete and also should be aggregated
-				if(currentPeriod != null && currentPeriod.getEndTimestamp() <= new UTCTimePeriod(aggregationStartTime, aggrPeriodLength).getPreviosPeriod().getEndTimestamp()){
+				if(currentPeriod != null &&
+                        currentPeriod.getEndTimestamp() <= new UTCTimePeriod(aggregationStartTime, aggrPeriodLength).getPreviosPeriod().getEndTimestamp()){
 					saveData(preparedInsertStmt, confidenceSum, sum, samples, currentPeriod, ++highestSequenceId);
 				}
 				
@@ -247,7 +258,11 @@ public class SensorDataAggregatorDaemon implements HalDaemon {
 					aggrConfidence = 1; // ignore confidence for average
 					break;
 			}
-			logger.finer("saved period: " + currentPeriod + ", data: " + data + ", confidence: " + aggrConfidence + ", samples: " + samples + ", aggrMethod: " + aggrMethod);
+			logger.finer("Saved period: " + currentPeriod +
+                    ", data: " + data +
+                    ", confidence: " + aggrConfidence +
+                    ", samples: " + samples +
+                    ", aggrMethod: " + aggrMethod);
 
 			preparedInsertStmt.setLong(1, sensorId);
 			preparedInsertStmt.setLong(2, sequenceId);