diff --git a/moto/core/utils.py b/moto/core/utils.py
index 946dd589..7d4a9d41 100644
--- a/moto/core/utils.py
+++ b/moto/core/utils.py
@@ -170,6 +170,10 @@ def iso_8601_datetime_with_milliseconds(datetime):
     return datetime.strftime("%Y-%m-%dT%H:%M:%S.%f")[:-3] + 'Z'
 
 
+def iso_8601_datetime_without_milliseconds(datetime):
+    return datetime.strftime("%Y-%m-%dT%H:%M:%S") + 'Z'
+
+
 def rfc_1123_datetime(datetime):
     RFC1123 = '%a, %d %b %Y %H:%M:%S GMT'
     return datetime.strftime(RFC1123)
diff --git a/moto/iam/models.py b/moto/iam/models.py
index 456dce4a..c7142fb5 100644
--- a/moto/iam/models.py
+++ b/moto/iam/models.py
@@ -4,6 +4,7 @@ from datetime import datetime
 
 import pytz
 from moto.core import BaseBackend, BaseModel
+from moto.core.utils import iso_8601_datetime_without_milliseconds
 
 from .exceptions import IAMNotFoundException, IAMConflictException, IAMReportNotPresentException
 from .utils import random_access_key, random_alphanumeric, random_resource_id, random_policy_id
@@ -235,10 +236,7 @@ class User(BaseModel):
         self.name = name
         self.id = random_resource_id()
         self.path = path if path else "/"
-        self.created = datetime.strftime(
-            datetime.utcnow(),
-            "%Y-%m-%d-%H-%M-%S"
-        )
+        self.created = datetime.utcnow()
         self.mfa_devices = {}
         self.policies = {}
         self.access_keys = []
@@ -248,6 +246,10 @@ class User(BaseModel):
     def arn(self):
         return "arn:aws:iam::{0}:user{1}{2}".format(ACCOUNT_ID, self.path, self.name)
 
+    @property
+    def created_iso_8601(self):
+        return iso_8601_datetime_without_milliseconds(self.created)
+
     def get_policy(self, policy_name):
         policy_json = None
         try:
@@ -310,7 +312,7 @@ class User(BaseModel):
 
     def to_csv(self):
         date_format = '%Y-%m-%dT%H:%M:%S+00:00'
-        date_created = datetime.strptime(self.created, '%Y-%m-%d-%H-%M-%S')
+        date_created = self.created
         # aagrawal,arn:aws:iam::509284790694:user/aagrawal,2014-09-01T22:28:48+00:00,true,2014-11-12T23:36:49+00:00,2014-09-03T18:59:00+00:00,N/A,false,true,2014-09-01T22:28:48+00:00,false,N/A,false,N/A,false,N/A
         if not self.password:
             password_enabled = 'false'
diff --git a/moto/iam/responses.py b/moto/iam/responses.py
index c56090cf..8e19b3aa 100644
--- a/moto/iam/responses.py
+++ b/moto/iam/responses.py
@@ -823,7 +823,7 @@ LIST_USERS_TEMPLATE = """<{{ action }}UsersResponse>
              <UserId>{{ user.id }}</UserId>
              <Path>{{ user.path }}</Path>
              <UserName>{{ user.name }}</UserName>
-             <CreateDate>{{ user.created }}</CreateDate>
+             <CreateDate>{{ user.created_iso_8601 }}</CreateDate>
              <Arn>{{ user.arn }}</Arn>
          </member>
          {% endfor %}