diff --git a/safe_transaction_service/account_abstraction/constants.py b/safe_transaction_service/account_abstraction/constants.py
index 375ef827c..0a39d203c 100644
--- a/safe_transaction_service/account_abstraction/constants.py
+++ b/safe_transaction_service/account_abstraction/constants.py
@@ -17,6 +17,7 @@
 
 from hexbytes import HexBytes
 
+USER_OPERATION_NUMBER_TOPICS = 4
 USER_OPERATION_EVENT_TOPICS = {
     HexBytes("0x49628fd1471006c1482da88028e9ce4dbb080b815c9b0344d39e5a8e6ec1419f")
 }
diff --git a/safe_transaction_service/account_abstraction/exceptions.py b/safe_transaction_service/account_abstraction/exceptions.py
deleted file mode 100644
index e69de29bb..000000000
diff --git a/safe_transaction_service/account_abstraction/services/aa_processor_service.py b/safe_transaction_service/account_abstraction/services/aa_processor_service.py
index 8f73255c2..c1c92967e 100644
--- a/safe_transaction_service/account_abstraction/services/aa_processor_service.py
+++ b/safe_transaction_service/account_abstraction/services/aa_processor_service.py
@@ -22,7 +22,7 @@
 
 from safe_transaction_service.history import models as history_models
 
-from ..constants import USER_OPERATION_EVENT_TOPICS
+from ..constants import USER_OPERATION_EVENT_TOPICS, USER_OPERATION_NUMBER_TOPICS
 from ..models import SafeOperation as SafeOperationModel
 from ..models import SafeOperationConfirmation as SafeOperationConfirmationModel
 from ..models import UserOperation as UserOperationModel
@@ -86,7 +86,7 @@ def get_user_operation_logs(
             log
             for log in logs
             if (
-                len(log["topics"]) == 4
+                len(log["topics"]) == USER_OPERATION_NUMBER_TOPICS
                 and HexBytes(log["topics"][0]) in USER_OPERATION_EVENT_TOPICS
                 and fast_to_checksum_address(log["address"])
                 in self.supported_entry_points  # Only index supported entryPoints
diff --git a/safe_transaction_service/account_abstraction/tests/test_views.py b/safe_transaction_service/account_abstraction/tests/test_views.py
index 2b15e23a1..840c07235 100644
--- a/safe_transaction_service/account_abstraction/tests/test_views.py
+++ b/safe_transaction_service/account_abstraction/tests/test_views.py
@@ -1,4 +1,3 @@
-import datetime
 import logging
 from unittest import mock
 from unittest.mock import MagicMock
@@ -25,20 +24,14 @@
 from gnosis.safe.safe_signature import SafeSignatureEOA
 from gnosis.safe.tests.safe_test_case import SafeTestCaseMixin
 
+from safe_transaction_service.utils.utils import datetime_to_str
+
 from .. import models
 from . import factories
 
 logger = logging.getLogger(__name__)
 
 
-# FIXME Refactor datetime_to_str
-def datetime_to_str(value: datetime.datetime) -> str:
-    value = value.isoformat()
-    if value.endswith("+00:00"):
-        value = value[:-6] + "Z"
-    return value
-
-
 class TestAccountAbstractionViews(SafeTestCaseMixin, APITestCase):
     def test_safe_operation_view(self):
         random_safe_operation_hash = (
diff --git a/safe_transaction_service/safe_messages/tests/test_views.py b/safe_transaction_service/safe_messages/tests/test_views.py
index 9ecb5e904..466b2eb5c 100644
--- a/safe_transaction_service/safe_messages/tests/test_views.py
+++ b/safe_transaction_service/safe_messages/tests/test_views.py
@@ -1,4 +1,3 @@
-import datetime
 import logging
 from unittest import mock
 from unittest.mock import MagicMock
@@ -26,19 +25,13 @@
     SafeMessageConfirmationFactory,
     SafeMessageFactory,
 )
+from safe_transaction_service.utils.utils import datetime_to_str
 
 from .mocks import get_eip712_payload_mock
 
 logger = logging.getLogger(__name__)
 
 
-def datetime_to_str(value: datetime.datetime) -> str:
-    value = value.isoformat()
-    if value.endswith("+00:00"):
-        value = value[:-6] + "Z"
-    return value
-
-
 class TestMessageViews(SafeTestCaseMixin, APITestCase):
     def test_safe_message_view(self):
         random_safe_message_hash = (
diff --git a/safe_transaction_service/utils/utils.py b/safe_transaction_service/utils/utils.py
index abe971d6f..746556287 100644
--- a/safe_transaction_service/utils/utils.py
+++ b/safe_transaction_service/utils/utils.py
@@ -1,3 +1,4 @@
+import datetime
 import socket
 from functools import wraps
 from itertools import islice
@@ -80,3 +81,14 @@ def wrapper(*args, **kwargs):
 
 def parse_boolean_query_param(value: Union[bool, str, int]) -> bool:
     return value in (True, "True", "true", "1", 1)
+
+
+def datetime_to_str(value: datetime.datetime) -> str:
+    """
+    :param value: `datetime.datetime` value
+    :return: ``ISO 8601`` date with ``Z`` format
+    """
+    value = value.isoformat()
+    if value.endswith("+00:00"):
+        value = value[:-6] + "Z"
+    return value