diff --git a/rowers/management/commands/processalerts.py b/rowers/management/commands/processalerts.py
index febfe20f..12937fcd 100644
--- a/rowers/management/commands/processalerts.py
+++ b/rowers/management/commands/processalerts.py
@@ -45,7 +45,7 @@ class Command(BaseCommand):
 
             # explanatorytexts
             othertexts = [alert.description()]
-            
+
             # send email
             job = myqueue(queue,handle_send_email_alert,
                           alert.manager.email,
@@ -58,11 +58,11 @@ class Command(BaseCommand):
 
             # advance next_run
             if not testing:
-                alert.next_run = datetime.date.today() + datetime.timedelta(days=alert.period)
+                alert.next_run = datetime.date.today() + datetime.timedelta(days=alert.period-1)
                 alert.save()
 
         if testing:
             print('{nr} alerts found'.format(nr = len(todaysalerts)))
-        
+
         self.stdout.write(self.style.SUCCESS(
             'Successfully processed alerts'))