diff --git a/moto/iam/models.py b/moto/iam/models.py
index 8d6de8062..7d2c05430 100644
--- a/moto/iam/models.py
+++ b/moto/iam/models.py
@@ -474,12 +474,8 @@ class AWSManagedPolicy(ManagedPolicy):
             default_version_id=data.get("DefaultVersionId"),
             path=data.get("Path"),
             document=json.dumps(data.get("Document")),
-            create_date=datetime.strptime(
-                data.get("CreateDate"), "%Y-%m-%dT%H:%M:%S+00:00"  # type: ignore[arg-type]
-            ),
-            update_date=datetime.strptime(
-                data.get("UpdateDate"), "%Y-%m-%dT%H:%M:%S+00:00"  # type: ignore[arg-type]
-            ),
+            create_date=datetime.fromisoformat(data["CreateDate"]),
+            update_date=datetime.fromisoformat(data["UpdateDate"]),
         )
 
     @property
diff --git a/moto/iam/utils.py b/moto/iam/utils.py
index a31aed6f2..9f17d3ff3 100644
--- a/moto/iam/utils.py
+++ b/moto/iam/utils.py
@@ -38,16 +38,12 @@ def generate_access_key_id_from_account_id(
 
 
 def random_alphanumeric(length: int) -> str:
-    return "".join(
-        str(random.choice(string.ascii_letters + string.digits + "+" + "/"))
-        for _ in range(length)
-    )
+    options = string.ascii_letters + string.digits + "+" + "/"
+    return "".join(random.choices(options, k=length))
 
 
 def random_resource_id(size: int = 20) -> str:
-    chars = list(range(10)) + list(string.ascii_lowercase)
-
-    return "".join(str(random.choice(chars)) for x in range(size))
+    return "".join(random.choices(string.ascii_lowercase + string.digits, k=size))
 
 
 def random_role_id(account_id: str) -> str:
@@ -57,12 +53,8 @@ def random_role_id(account_id: str) -> str:
 
 
 def random_access_key() -> str:
-    return "".join(
-        str(random.choice(string.ascii_uppercase + string.digits)) for _ in range(16)
-    )
+    return "".join(random.choices(string.ascii_uppercase + string.digits, k=16))
 
 
 def random_policy_id() -> str:
-    return "A" + "".join(
-        random.choice(string.ascii_uppercase + string.digits) for _ in range(20)
-    )
+    return "A" + "".join(random.choices(string.ascii_uppercase + string.digits, k=20))