diff --git a/src/pretix/base/models/orders.py b/src/pretix/base/models/orders.py
index c3327fa5c5..f7268aecec 100644
--- a/src/pretix/base/models/orders.py
+++ b/src/pretix/base/models/orders.py
@@ -541,7 +541,7 @@ class Order(LockModel, LoggedModel):
         self.save(update_fields=['last_modified'])
 
     def set_expires(self, now_dt=None, subevents=None):
-        now_dt = now_dt or now()
+        now_dt = now_dt or time_machine_now()
         tz = ZoneInfo(self.event.settings.timezone)
         mode = self.event.settings.get('payment_term_mode')
         if mode == 'days':
diff --git a/src/pretix/base/services/orders.py b/src/pretix/base/services/orders.py
index 843c0bdaa3..da2b1dcd5c 100644
--- a/src/pretix/base/services/orders.py
+++ b/src/pretix/base/services/orders.py
@@ -106,6 +106,7 @@ from pretix.celery_app import app
 from pretix.helpers import OF_SELF
 from pretix.helpers.models import modelcopy
 from pretix.helpers.periodic import minimum_interval
+from pretix.presale.timemachine import time_machine_now
 from pretix.testutils.middleware import debugflags_var
 
 
@@ -1163,7 +1164,7 @@ def _perform_order(event: Event, payment_requests: List[dict], position_ids: Lis
     warnings = []
     any_payment_failed = False
 
-    now_dt = now()
+    now_dt = time_machine_now()
     err_out = None
     with transaction.atomic(durable=True):
         positions = list(