diff --git a/models/database/base.py b/models/database/base.py
index f14073a2..6ccd1b76 100644
--- a/models/database/base.py
+++ b/models/database/base.py
@@ -5,14 +5,20 @@ from sqlalchemy import Column, DateTime, ForeignKey, Integer
 from app.core.database import Base
 
 
+def _utc_now() -> datetime:
+    return datetime.now(UTC)
+
+
 class TimestampMixin:
     """Mixin to add created_at and updated_at timestamps to models"""
 
-    created_at = Column(DateTime, default=datetime.now(UTC), nullable=False)
+    # Pass the callable, not its result. Otherwise the default is evaluated
+    # once at module import and every row gets the same timestamp.
+    created_at = Column(DateTime, default=_utc_now, nullable=False)
     updated_at = Column(
         DateTime,
-        default=datetime.now(UTC),
-        onupdate=datetime.now(UTC),
+        default=_utc_now,
+        onupdate=_utc_now,
         nullable=False,
     )