diff --git a/src/agenda_culturel/calendar.py b/src/agenda_culturel/calendar.py
index ca39f5c..9b88dd2 100644
--- a/src/agenda_culturel/calendar.py
+++ b/src/agenda_culturel/calendar.py
@@ -28,6 +28,7 @@ def daterange(start, end, step=timedelta(1)):
 
 class DayInCalendar:
     midnight = time(0, 0, 0)
+    cats = None
 
     def __init__(self, d, on_requested_interval=True):
         self.date = d
@@ -138,9 +139,10 @@ class DayInCalendar:
 
     def events_by_category_ordered(self):
         from .models import Category
-        cats = Category.objects.order_by('position')
+        if DayInCalendar.cats is None:
+            DayInCalendar.cats = Category.objects.order_by('position')
         result = []
-        for c in cats:
+        for c in DayInCalendar.cats:
             if c.name in self.events_by_category:
                 result.append((c.name, self.events_by_category[c.name]))
         return result