#687648 from Robert Schuppenies: use classic division.
diff --git a/Demo/scripts/unbirthday.py b/Demo/scripts/unbirthday.py
index 2d0b8e5..8ed9084 100755
--- a/Demo/scripts/unbirthday.py
+++ b/Demo/scripts/unbirthday.py
@@ -92,9 +92,9 @@
     # even though that day never actually existed and the calendar
     # was different then...
     days = year*365                 # years, roughly
-    days = days + (year+3)/4        # plus leap years, roughly
-    days = days - (year+99)/100     # minus non-leap years every century
-    days = days + (year+399)/400    # plus leap years every 4 centirues
+    days = days + (year+3)//4        # plus leap years, roughly
+    days = days - (year+99)//100     # minus non-leap years every century
+    days = days + (year+399)//400    # plus leap years every 4 centirues
     for i in range(1, month):
         if i == 2 and calendar.isleap(year):
             days = days + 29