diff --git a/censys/asm/clouds.py b/censys/asm/clouds.py
index 19c2f90d..06a3b6e0 100644
--- a/censys/asm/clouds.py
+++ b/censys/asm/clouds.py
@@ -1,25 +1,8 @@
 """Interact with the Censys Clouds API."""
-import datetime
-from typing import Union
-
+from ..common.types import Datetime
+from ..common.utils import format_iso8601
 from .api import CensysAsmAPI
 
-Since = Union[str, datetime.date, datetime.datetime]
-
-
-def format_since_date(since: Since) -> str:
-    """Formats since date as ISO 8601 format.
-
-    Args:
-        since (Since): Date.
-
-    Returns:
-        str: ISO 8601 formatted date string.
-    """
-    if isinstance(since, (datetime.date, datetime.datetime)):
-        return since.strftime("%Y-%m-%d")
-    return since
-
 
 class Clouds(CensysAsmAPI):
     """Clouds API class."""
@@ -28,55 +11,55 @@ class Clouds(CensysAsmAPI):
 
     def get_host_counts(
         self,
-        since: Since,
+        since: Datetime,
     ) -> dict:
         """Retrieve host counts by cloud.
 
         Hosts found after the date provided in the `since` parameter will be included in the new asset counts.
 
         Args:
-            since (Since): Date to include hosts from.
+            since (Datetime): Date to include hosts from.
 
         Returns:
             dict: Host count result.
         """
-        since = format_since_date(since)
+        since = format_iso8601(since)
         return self._get(f"{self.base_path}/hostCounts/{since}")
 
-    def get_domain_counts(self, since: Since) -> dict:
+    def get_domain_counts(self, since: Datetime) -> dict:
         """Retrieve domain counts by cloud.
 
         Args:
-            since (Since): Date to include domains from.
+            since (Datetime): Date to include domains from.
 
         Returns:
             dict: Domain count result.
         """
-        since = format_since_date(since)
+        since = format_iso8601(since)
         return self._get(f"{self.base_path}/domainCounts/{since}")
 
-    def get_object_store_counts(self, since: Since) -> dict:
+    def get_object_store_counts(self, since: Datetime) -> dict:
         """Retrieve object store counts by cloud.
 
         Args:
-            since (Since): Date to include object stores from.
+            since (Datetime): Date to include object stores from.
 
         Returns:
             dict: Object store count result.
         """
-        since = format_since_date(since)
+        since = format_iso8601(since)
         return self._get(f"{self.base_path}/objectStoreCounts/{since}")
 
-    def get_subdomain_counts(self, since: Since) -> dict:
+    def get_subdomain_counts(self, since: Datetime) -> dict:
         """Retrieve subdomain counts by cloud.
 
         Args:
-            since (Since): Date to include subdomains from.
+            since (Datetime): Date to include subdomains from.
 
         Returns:
             dict: Subdomain count result.
         """
-        since = format_since_date(since)
+        since = format_iso8601(since)
         return self._get(f"{self.base_path}/subdomainCounts/{since}")
 
     def get_unknown_counts(self) -> dict:
diff --git a/censys/common/utils.py b/censys/common/utils.py
index 1c54b729..4099218a 100644
--- a/censys/common/utils.py
+++ b/censys/common/utils.py
@@ -17,3 +17,17 @@ def format_rfc3339(time: Datetime) -> str:
     if isinstance(time, (datetime.date, datetime.datetime)):
         time = time.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
     return time
+
+
+def format_iso8601(time: Datetime) -> str:
+    """Formats a datetime object into an ISO8601 string.
+
+    Args:
+        time (Datetime): Datetime object to format.
+
+    Returns:
+        str: ISO8601 formatted string.
+    """
+    if isinstance(time, (datetime.date, datetime.datetime)):
+        return time.strftime("%Y-%m-%d")
+    return time
diff --git a/tests/asm/test_clouds.py b/tests/asm/test_clouds.py
index 61c2ddf1..53362218 100644
--- a/tests/asm/test_clouds.py
+++ b/tests/asm/test_clouds.py
@@ -1,12 +1,8 @@
-import datetime
-
 import responses
-from parameterized import parameterized
 
 from ..utils import CensysTestCase
 from .utils import V1_URL
 from censys.asm.client import AsmClient
-from censys.asm.clouds import format_since_date
 
 TEST_COUNT_JSON = {
     "totalAssetCount": 0,
@@ -24,17 +20,6 @@ def setUp(self):
         super().setUp()
         self.client = AsmClient(self.api_key)
 
-    @parameterized.expand(
-        [
-            ["2021-01-01", "2021-01-01"],
-            [datetime.date(2021, 1, 1), "2021-01-01"],
-            [datetime.datetime(2021, 1, 1, 12, 15, 20, 40), "2021-01-01"],
-        ]
-    )
-    def test_format_since_date(self, since, actual):
-        # Actual call/assertions
-        assert format_since_date(since) == actual
-
     def test_get_host_counts(self):
         # Setup response
         self.responses.add(
diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 00000000..23f4f7c2
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,31 @@
+import datetime
+import unittest
+
+from parameterized import parameterized
+
+from censys.common.utils import format_iso8601, format_rfc3339
+
+
+class UtilsTest(unittest.TestCase):
+    @parameterized.expand(
+        [
+            ["2021-01-01", "2021-01-01"],
+            [datetime.date(2021, 1, 1), "2021-01-01T00:00:00.000000Z"],
+            [
+                datetime.datetime(2021, 1, 1, 12, 15, 20, 40),
+                "2021-01-01T12:15:20.000040Z",
+            ],
+        ]
+    )
+    def test_format_rfc3339(self, since, actual):
+        assert format_rfc3339(since) == actual
+
+    @parameterized.expand(
+        [
+            ["2021-01-01", "2021-01-01"],
+            [datetime.date(2021, 1, 1), "2021-01-01"],
+            [datetime.datetime(2021, 1, 1, 12, 15, 20, 40), "2021-01-01"],
+        ]
+    )
+    def test_format_iso8601(self, since, actual):
+        assert format_iso8601(since) == actual