diff --git a/tests/test_stock_detail_realtime.py b/tests/test_stock_detail_realtime.py
index b33743a..010d701 100644
--- a/tests/test_stock_detail_realtime.py
+++ b/tests/test_stock_detail_realtime.py
@@ -46,7 +46,7 @@ class RealtimeClientStub:
 
 
 class FixedMarketDatetime(datetime):
-    fixed_now = datetime.now().astimezone().replace(hour=10, minute=30, second=0, microsecond=0)
+    fixed_now = datetime(2026, 7, 31, 10, 30).astimezone()
 
     @classmethod
     def now(cls, tz=None):
@@ -54,7 +54,7 @@ class FixedMarketDatetime(datetime):
 
 
 class FixedPreopenDatetime(datetime):
-    fixed_now = datetime.now().astimezone().replace(hour=8, minute=45, second=0, microsecond=0)
+    fixed_now = datetime(2026, 7, 31, 8, 45).astimezone()
 
     @classmethod
     def now(cls, tz=None):