diff -r 0690d715385d -r 67f48e288102 helpers.py
--- a/helpers.py	Wed Feb 11 04:57:55 2009 +0200
+++ b/helpers.py	Wed Feb 11 21:49:35 2009 +0200
@@ -200,4 +200,18 @@
                 value
             ) for key, value in key_values
         )
+    
+    def prev_date (self, date) :
+        """
+            Returns the previous date for the given datetime-date
+        """
 
+        return datetime.datetime(date.year, date.month, date.day, tzinfo=date.tzinfo) - datetime.timedelta(days=1)
+
+    def next_date (self, date) :
+        """
+            Returns the previous date for the given datetime-date
+        """
+
+        return datetime.datetime(date.year, date.month, date.day, tzinfo=date.tzinfo) + datetime.timedelta(days=1)
+