diff --git a/mpwo_api/mpwo_api/activities/models.py b/mpwo_api/mpwo_api/activities/models.py
index 1b016a5d..ac7b0428 100644
--- a/mpwo_api/mpwo_api/activities/models.py
+++ b/mpwo_api/mpwo_api/activities/models.py
@@ -33,8 +33,10 @@ class Activity(db.Model):
         db.ForeignKey('sports.id'),
         nullable=False)
     gpx = db.Column(db.String(255), nullable=True)
-    creation_date = db.Column(db.DateTime, default=datetime.datetime.now)
-    modification_date = db.Column(db.DateTime, onupdate=datetime.datetime.now)
+    creation_date = db.Column(
+        db.DateTime, default=datetime.datetime.utcnow)
+    modification_date = db.Column(
+        db.DateTime, onupdate=datetime.datetime.utcnow)
     activity_date = db.Column(db.DateTime, nullable=False)
     duration = db.Column(db.Interval, nullable=False)
     pauses = db.Column(db.Interval, nullable=True)
diff --git a/mpwo_api/mpwo_api/users/models.py b/mpwo_api/mpwo_api/users/models.py
index 7e0e72c0..8878b76a 100644
--- a/mpwo_api/mpwo_api/users/models.py
+++ b/mpwo_api/mpwo_api/users/models.py
@@ -28,7 +28,7 @@ class User(db.Model):
 
     def __init__(
             self, username, email, password,
-            created_at=datetime.datetime.now()):
+            created_at=datetime.datetime.utcnow()):
         self.username = username
         self.email = email
         self.password = bcrypt.generate_password_hash(