=== modified file 'dhis-2/dhis-api/src/main/java/org/hisp/dhis/period/PeriodService.java'
--- dhis-2/dhis-api/src/main/java/org/hisp/dhis/period/PeriodService.java	2009-06-02 12:13:35 +0000
+++ dhis-2/dhis-api/src/main/java/org/hisp/dhis/period/PeriodService.java	2010-01-28 19:59:57 +0000
@@ -226,6 +226,15 @@
      */
     Period getRelativePeriod( Date date, int months );
 
+    /**
+     * Returns historyLength number of Periods chronologically ending with lastPeriod.
+     * 
+     * @param lastPeriod the last Period in the provided collection.
+     * @param historyLength the number of Periods in the provided collection.
+     * @return a collection of Periods.
+     */
+    Collection<Period> getPeriods( Period lastPeriod, int historyLength );
+    
     // -------------------------------------------------------------------------
     // PeriodType
     // -------------------------------------------------------------------------

=== modified file 'dhis-2/dhis-services/dhis-service-core/src/main/java/org/hisp/dhis/period/DefaultPeriodService.java'
--- dhis-2/dhis-services/dhis-service-core/src/main/java/org/hisp/dhis/period/DefaultPeriodService.java	2009-11-26 14:02:44 +0000
+++ dhis-2/dhis-services/dhis-service-core/src/main/java/org/hisp/dhis/period/DefaultPeriodService.java	2010-01-28 19:59:57 +0000
@@ -30,6 +30,7 @@
 import java.util.ArrayList;
 import java.util.Calendar;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Date;
 import java.util.Iterator;
 import java.util.List;
@@ -294,6 +295,30 @@
 
         return period;
     }
+    
+    public Collection<Period> getPeriods( Period lastPeriod, int historyLength )
+    {
+        List<Period> periods = new ArrayList<Period>( historyLength );
+
+        CalendarPeriodType periodType = (CalendarPeriodType) lastPeriod.getPeriodType();
+
+        Period period = lastPeriod;
+        
+        Period p = new Period();
+
+        for ( int i = 0; i < historyLength; ++i )
+        {
+            p = getPeriodFromDates( period.getStartDate(), period.getEndDate(), periodType );
+            
+            periods.add( p != null ? p : period );
+            
+            period = periodType.getPreviousPeriod( period );
+        }
+
+        Collections.reverse( periods );
+
+        return periods;
+    }
 
     // -------------------------------------------------------------------------
     // PeriodType