diff --git a/moto/iam/models.py b/moto/iam/models.py
index 095bbab29..cacc5ebb3 100644
--- a/moto/iam/models.py
+++ b/moto/iam/models.py
@@ -8,10 +8,9 @@ import re
 from cryptography import x509
 from cryptography.hazmat.backends import default_backend
 
-import pytz
 from moto.core.exceptions import RESTError
 from moto.core import BaseBackend, BaseModel
-from moto.core.utils import iso_8601_datetime_without_milliseconds
+from moto.core.utils import iso_8601_datetime_without_milliseconds, iso_8601_datetime_with_milliseconds
 
 from .aws_managed_policies import aws_managed_policies_data
 from .exceptions import IAMNotFoundException, IAMConflictException, IAMReportNotPresentException, MalformedCertificate, \
@@ -28,11 +27,15 @@ class MFADevice(object):
                  serial_number,
                  authentication_code_1,
                  authentication_code_2):
-        self.enable_date = datetime.now(pytz.utc)
+        self.enable_date = datetime.utcnow()
         self.serial_number = serial_number
         self.authentication_code_1 = authentication_code_1
         self.authentication_code_2 = authentication_code_2
 
+    @property
+    def enabled_iso_8601(self):
+        return iso_8601_datetime_without_milliseconds(self.enable_date)
+
 
 class Policy(BaseModel):
     is_attachable = False
@@ -58,8 +61,16 @@ class Policy(BaseModel):
             self.next_version_num = 2
         self.versions = [PolicyVersion(self.arn, document, True)]
 
-        self.create_datetime = datetime.now(pytz.utc)
-        self.update_datetime = datetime.now(pytz.utc)
+        self.create_date = datetime.utcnow()
+        self.update_date = datetime.utcnow()
+
+    @property
+    def created_iso_8601(self):
+        return iso_8601_datetime_with_milliseconds(self.create_date)
+
+    @property
+    def updated_iso_8601(self):
+        return iso_8601_datetime_with_milliseconds(self.update_date)
 
 
 class SAMLProvider(BaseModel):
@@ -83,7 +94,11 @@ class PolicyVersion(object):
         self.is_default = is_default
         self.version_id = 'v1'
 
-        self.create_datetime = datetime.now(pytz.utc)
+        self.create_date = datetime.utcnow()
+
+    @property
+    def created_iso_8601(self):
+        return iso_8601_datetime_with_milliseconds(self.create_date)
 
 
 class ManagedPolicy(Policy):
@@ -139,11 +154,15 @@ class Role(BaseModel):
         self.path = path or '/'
         self.policies = {}
         self.managed_policies = {}
-        self.create_date = datetime.now(pytz.utc)
+        self.create_date = datetime.utcnow()
         self.tags = {}
         self.description = ""
         self.permissions_boundary = permissions_boundary
 
+    @property
+    def created_iso_8601(self):
+        return iso_8601_datetime_with_milliseconds(self.create_date)
+
     @classmethod
     def create_from_cloudformation_json(cls, resource_name, cloudformation_json, region_name):
         properties = cloudformation_json['Properties']
@@ -198,7 +217,11 @@ class InstanceProfile(BaseModel):
         self.name = name
         self.path = path or '/'
         self.roles = roles if roles else []
-        self.create_date = datetime.now(pytz.utc)
+        self.create_date = datetime.utcnow()
+
+    @property
+    def created_iso_8601(self):
+        return iso_8601_datetime_with_milliseconds(self.create_date)
 
     @classmethod
     def create_from_cloudformation_json(cls, resource_name, cloudformation_json, region_name):
@@ -250,9 +273,13 @@ class SigningCertificate(BaseModel):
         self.id = id
         self.user_name = user_name
         self.body = body
-        self.upload_date = datetime.strftime(datetime.utcnow(), "%Y-%m-%d-%H-%M-%S")
+        self.upload_date = datetime.utcnow()
         self.status = 'Active'
 
+    @property
+    def uploaded_iso_8601(self):
+        return iso_8601_datetime_without_milliseconds(self.upload_date)
+
 
 class AccessKey(BaseModel):
 
@@ -261,14 +288,16 @@ class AccessKey(BaseModel):
         self.access_key_id = random_access_key()
         self.secret_access_key = random_alphanumeric(32)
         self.status = 'Active'
-        self.create_date = datetime.strftime(
-            datetime.utcnow(),
-            "%Y-%m-%dT%H:%M:%SZ"
-        )
-        self.last_used = datetime.strftime(
-            datetime.utcnow(),
-            "%Y-%m-%dT%H:%M:%SZ"
-        )
+        self.create_date = datetime.utcnow()
+        self.last_used = datetime.utcnow()
+
+    @property
+    def created_iso_8601(self):
+        return iso_8601_datetime_without_milliseconds(self.create_date)
+
+    @property
+    def last_used_iso_8601(self):
+        return iso_8601_datetime_without_milliseconds(self.last_used)
 
     def get_cfn_attribute(self, attribute_name):
         from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
@@ -283,15 +312,16 @@ class Group(BaseModel):
         self.name = name
         self.id = random_resource_id()
         self.path = path
-        self.created = datetime.strftime(
-            datetime.utcnow(),
-            "%Y-%m-%d-%H-%M-%S"
-        )
+        self.create_date = datetime.utcnow()
 
         self.users = []
         self.managed_policies = {}
         self.policies = {}
 
+    @property
+    def created_iso_8601(self):
+        return iso_8601_datetime_with_milliseconds(self.create_date)
+
     def get_cfn_attribute(self, attribute_name):
         from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
         if attribute_name == 'Arn':
@@ -306,10 +336,6 @@ class Group(BaseModel):
         else:
             return "arn:aws:iam::{0}:group/{1}/{2}".format(ACCOUNT_ID, self.path, self.name)
 
-    @property
-    def create_date(self):
-        return self.created
-
     def get_policy(self, policy_name):
         try:
             policy_json = self.policies[policy_name]
@@ -335,7 +361,7 @@ class User(BaseModel):
         self.name = name
         self.id = random_resource_id()
         self.path = path if path else "/"
-        self.created = datetime.utcnow()
+        self.create_date = datetime.utcnow()
         self.mfa_devices = {}
         self.policies = {}
         self.managed_policies = {}
@@ -350,7 +376,7 @@ class User(BaseModel):
 
     @property
     def created_iso_8601(self):
-        return iso_8601_datetime_without_milliseconds(self.created)
+        return iso_8601_datetime_with_milliseconds(self.create_date)
 
     def get_policy(self, policy_name):
         policy_json = None
@@ -421,7 +447,7 @@ class User(BaseModel):
 
     def to_csv(self):
         date_format = '%Y-%m-%dT%H:%M:%S+00:00'
-        date_created = self.created
+        date_created = self.create_date
         # 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'
@@ -1050,7 +1076,7 @@ class IAMBackend(BaseBackend):
             if key.access_key_id == access_key_id:
                 return {
                     'user_name': key.user_name,
-                    'last_used': key.last_used
+                    'last_used': key.last_used_iso_8601,
                 }
         else:
             raise IAMNotFoundException(
diff --git a/moto/iam/responses.py b/moto/iam/responses.py
index 8d2a557cb..05624101a 100644
--- a/moto/iam/responses.py
+++ b/moto/iam/responses.py
@@ -818,12 +818,12 @@ CREATE_POLICY_TEMPLATE = """<CreatePolicyResponse>
     <Policy>
       <Arn>{{ policy.arn }}</Arn>
       <AttachmentCount>{{ policy.attachment_count }}</AttachmentCount>
-      <CreateDate>{{ policy.create_datetime.isoformat() }}</CreateDate>
+      <CreateDate>{{ policy.created_iso_8601 }}</CreateDate>
       <DefaultVersionId>{{ policy.default_version_id }}</DefaultVersionId>
       <Path>{{ policy.path }}</Path>
       <PolicyId>{{ policy.id }}</PolicyId>
       <PolicyName>{{ policy.name }}</PolicyName>
-      <UpdateDate>{{ policy.update_datetime.isoformat() }}</UpdateDate>
+      <UpdateDate>{{ policy.updated_iso_8601 }}</UpdateDate>
     </Policy>
   </CreatePolicyResult>
   <ResponseMetadata>
@@ -841,8 +841,8 @@ GET_POLICY_TEMPLATE = """<GetPolicyResponse>
       <Path>{{ policy.path }}</Path>
       <Arn>{{ policy.arn }}</Arn>
       <AttachmentCount>{{ policy.attachment_count }}</AttachmentCount>
-      <CreateDate>{{ policy.create_datetime.isoformat() }}</CreateDate>
-      <UpdateDate>{{ policy.update_datetime.isoformat() }}</UpdateDate>
+      <CreateDate>{{ policy.created_iso_8601 }}</CreateDate>
+      <UpdateDate>{{ policy.updated_iso_8601 }}</UpdateDate>
     </Policy>
   </GetPolicyResult>
   <ResponseMetadata>
@@ -929,12 +929,12 @@ LIST_POLICIES_TEMPLATE = """<ListPoliciesResponse>
       <member>
         <Arn>{{ policy.arn }}</Arn>
         <AttachmentCount>{{ policy.attachment_count }}</AttachmentCount>
-        <CreateDate>{{ policy.create_datetime.isoformat() }}</CreateDate>
+        <CreateDate>{{ policy.created_iso_8601 }}</CreateDate>
         <DefaultVersionId>{{ policy.default_version_id }}</DefaultVersionId>
         <Path>{{ policy.path }}</Path>
         <PolicyId>{{ policy.id }}</PolicyId>
         <PolicyName>{{ policy.name }}</PolicyName>
-        <UpdateDate>{{ policy.update_datetime.isoformat() }}</UpdateDate>
+        <UpdateDate>{{ policy.updated_iso_8601 }}</UpdateDate>
       </member>
       {% endfor %}
     </Policies>
@@ -958,7 +958,7 @@ CREATE_INSTANCE_PROFILE_TEMPLATE = """<CreateInstanceProfileResponse xmlns="http
       <InstanceProfileName>{{ profile.name }}</InstanceProfileName>
       <Path>{{ profile.path }}</Path>
       <Arn>{{ profile.arn }}</Arn>
-      <CreateDate>{{ profile.create_date }}</CreateDate>
+      <CreateDate>{{ profile.created_iso_8601 }}</CreateDate>
     </InstanceProfile>
   </CreateInstanceProfileResult>
   <ResponseMetadata>
@@ -977,7 +977,7 @@ GET_INSTANCE_PROFILE_TEMPLATE = """<GetInstanceProfileResponse xmlns="https://ia
           <Arn>{{ role.arn }}</Arn>
           <RoleName>{{ role.name }}</RoleName>
           <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-          <CreateDate>{{ role.create_date }}</CreateDate>
+          <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
           <RoleId>{{ role.id }}</RoleId>
         </member>
         {% endfor %}
@@ -985,7 +985,7 @@ GET_INSTANCE_PROFILE_TEMPLATE = """<GetInstanceProfileResponse xmlns="https://ia
       <InstanceProfileName>{{ profile.name }}</InstanceProfileName>
       <Path>{{ profile.path }}</Path>
       <Arn>{{ profile.arn }}</Arn>
-      <CreateDate>{{ profile.create_date }}</CreateDate>
+      <CreateDate>{{ profile.created_iso_8601 }}</CreateDate>
     </InstanceProfile>
   </GetInstanceProfileResult>
   <ResponseMetadata>
@@ -1000,7 +1000,7 @@ CREATE_ROLE_TEMPLATE = """<CreateRoleResponse xmlns="https://iam.amazonaws.com/d
       <Arn>{{ role.arn }}</Arn>
       <RoleName>{{ role.name }}</RoleName>
       <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-      <CreateDate>{{ role.create_date }}</CreateDate>
+      <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
       <RoleId>{{ role.id }}</RoleId>
       {% if role.permissions_boundary %}
       <PermissionsBoundary>
@@ -1041,7 +1041,7 @@ UPDATE_ROLE_DESCRIPTION_TEMPLATE = """<UpdateRoleDescriptionResponse xmlns="http
       <Arn>{{ role.arn }}</Arn>
       <RoleName>{{ role.name }}</RoleName>
       <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-      <CreateDate>{{ role.create_date.isoformat() }}</CreateDate>
+      <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
       <RoleId>{{ role.id }}</RoleId>
       {% if role.tags %}
       <Tags>
@@ -1067,7 +1067,7 @@ GET_ROLE_TEMPLATE = """<GetRoleResponse xmlns="https://iam.amazonaws.com/doc/201
       <Arn>{{ role.arn }}</Arn>
       <RoleName>{{ role.name }}</RoleName>
       <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-      <CreateDate>{{ role.create_date }}</CreateDate>
+      <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
       <RoleId>{{ role.id }}</RoleId>
       {% if role.tags %}
       <Tags>
@@ -1108,7 +1108,7 @@ LIST_ROLES_TEMPLATE = """<ListRolesResponse xmlns="https://iam.amazonaws.com/doc
         <Arn>{{ role.arn }}</Arn>
         <RoleName>{{ role.name }}</RoleName>
         <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-        <CreateDate>{{ role.create_date }}</CreateDate>
+        <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
         <RoleId>{{ role.id }}</RoleId>
         {% if role.permissions_boundary %}
         <PermissionsBoundary>
@@ -1145,7 +1145,7 @@ CREATE_POLICY_VERSION_TEMPLATE = """<CreatePolicyVersionResponse xmlns="https://
       <Document>{{ policy_version.document }}</Document>
       <VersionId>{{ policy_version.version_id }}</VersionId>
       <IsDefaultVersion>{{ policy_version.is_default }}</IsDefaultVersion>
-      <CreateDate>{{ policy_version.create_datetime }}</CreateDate>
+      <CreateDate>{{ policy_version.created_iso_8601 }}</CreateDate>
     </PolicyVersion>
   </CreatePolicyVersionResult>
   <ResponseMetadata>
@@ -1159,7 +1159,7 @@ GET_POLICY_VERSION_TEMPLATE = """<GetPolicyVersionResponse xmlns="https://iam.am
       <Document>{{ policy_version.document }}</Document>
       <VersionId>{{ policy_version.version_id }}</VersionId>
       <IsDefaultVersion>{{ policy_version.is_default }}</IsDefaultVersion>
-      <CreateDate>{{ policy_version.create_datetime }}</CreateDate>
+      <CreateDate>{{ policy_version.created_iso_8601 }}</CreateDate>
     </PolicyVersion>
   </GetPolicyVersionResult>
   <ResponseMetadata>
@@ -1176,7 +1176,7 @@ LIST_POLICY_VERSIONS_TEMPLATE = """<ListPolicyVersionsResponse xmlns="https://ia
         <Document>{{ policy_version.document }}</Document>
         <VersionId>{{ policy_version.version_id }}</VersionId>
         <IsDefaultVersion>{{ policy_version.is_default }}</IsDefaultVersion>
-        <CreateDate>{{ policy_version.create_datetime }}</CreateDate>
+        <CreateDate>{{ policy_version.created_iso_8601 }}</CreateDate>
       </member>
       {% endfor %}
     </Versions>
@@ -1200,7 +1200,7 @@ LIST_INSTANCE_PROFILES_TEMPLATE = """<ListInstanceProfilesResponse xmlns="https:
             <Arn>{{ role.arn }}</Arn>
             <RoleName>{{ role.name }}</RoleName>
             <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-            <CreateDate>{{ role.create_date }}</CreateDate>
+            <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
             <RoleId>{{ role.id }}</RoleId>
           </member>
           {% endfor %}
@@ -1208,7 +1208,7 @@ LIST_INSTANCE_PROFILES_TEMPLATE = """<ListInstanceProfilesResponse xmlns="https:
         <InstanceProfileName>{{ instance.name }}</InstanceProfileName>
         <Path>{{ instance.path }}</Path>
         <Arn>{{ instance.arn }}</Arn>
-        <CreateDate>{{ instance.create_date }}</CreateDate>
+        <CreateDate>{{ instance.created_iso_8601 }}</CreateDate>
       </member>
       {% endfor %}
     </InstanceProfiles>
@@ -1287,7 +1287,7 @@ CREATE_GROUP_TEMPLATE = """<CreateGroupResponse>
          <GroupName>{{ group.name }}</GroupName>
          <GroupId>{{ group.id }}</GroupId>
          <Arn>{{ group.arn }}</Arn>
-         <CreateDate>{{ group.create_date }}</CreateDate>
+         <CreateDate>{{ group.created_iso_8601 }}</CreateDate>
       </Group>
    </CreateGroupResult>
    <ResponseMetadata>
@@ -1302,7 +1302,7 @@ GET_GROUP_TEMPLATE = """<GetGroupResponse>
          <GroupName>{{ group.name }}</GroupName>
          <GroupId>{{ group.id }}</GroupId>
          <Arn>{{ group.arn }}</Arn>
-         <CreateDate>{{ group.create_date }}</CreateDate>
+         <CreateDate>{{ group.created_iso_8601 }}</CreateDate>
       </Group>
       <Users>
         {% for user in group.users %}
@@ -1509,7 +1509,7 @@ LIST_ACCESS_KEYS_TEMPLATE = """<ListAccessKeysResponse>
             <UserName>{{ user_name }}</UserName>
             <AccessKeyId>{{ key.access_key_id }}</AccessKeyId>
             <Status>{{ key.status }}</Status>
-            <CreateDate>{{ key.create_date }}</CreateDate>
+            <CreateDate>{{ key.created_iso_8601 }}</CreateDate>
          </member>
         {% endfor %}
       </AccessKeyMetadata>
@@ -1577,7 +1577,7 @@ LIST_INSTANCE_PROFILES_FOR_ROLE_TEMPLATE = """<ListInstanceProfilesForRoleRespon
         <Arn>{{ role.arn }}</Arn>
         <RoleName>{{ role.name }}</RoleName>
         <AssumeRolePolicyDocument>{{ role.assume_policy_document }}</AssumeRolePolicyDocument>
-        <CreateDate>{{ role.create_date }}</CreateDate>
+        <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
         <RoleId>{{ role.id }}</RoleId>
       </member>
       {% endfor %}
@@ -1585,7 +1585,7 @@ LIST_INSTANCE_PROFILES_FOR_ROLE_TEMPLATE = """<ListInstanceProfilesForRoleRespon
     <InstanceProfileName>{{ profile.name }}</InstanceProfileName>
     <Path>{{ profile.path }}</Path>
     <Arn>{{ profile.arn }}</Arn>
-    <CreateDate>{{ profile.create_date }}</CreateDate>
+    <CreateDate>{{ profile.created_iso_8601 }}</CreateDate>
     </member>
     {% endfor %}
   </InstanceProfiles>
@@ -1704,7 +1704,7 @@ GET_ACCOUNT_AUTHORIZATION_DETAILS_TEMPLATE = """<GetAccountAuthorizationDetailsR
         <GroupName>{{ group.name }}</GroupName>
         <Path>{{ group.path }}</Path>
         <Arn>{{ group.arn }}</Arn>
-        <CreateDate>{{ group.create_date }}</CreateDate>
+        <CreateDate>{{ group.created_iso_8601 }}</CreateDate>
         <GroupPolicyList>
         {% for policy in group.policies %}
             <member>
@@ -1754,7 +1754,7 @@ GET_ACCOUNT_AUTHORIZATION_DETAILS_TEMPLATE = """<GetAccountAuthorizationDetailsR
                 <Arn>{{ role.arn }}</Arn>
                 <RoleName>{{ role.name }}</RoleName>
                 <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-                <CreateDate>{{ role.create_date }}</CreateDate>
+                <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
                 <RoleId>{{ role.id }}</RoleId>
               </member>
               {% endfor %}
@@ -1762,7 +1762,7 @@ GET_ACCOUNT_AUTHORIZATION_DETAILS_TEMPLATE = """<GetAccountAuthorizationDetailsR
             <InstanceProfileName>{{ profile.name }}</InstanceProfileName>
             <Path>{{ profile.path }}</Path>
             <Arn>{{ profile.arn }}</Arn>
-            <CreateDate>{{ profile.create_date }}</CreateDate>
+            <CreateDate>{{ profile.created_iso_8601 }}</CreateDate>
             </member>
             {% endfor %}
         </InstanceProfileList>
@@ -1770,7 +1770,7 @@ GET_ACCOUNT_AUTHORIZATION_DETAILS_TEMPLATE = """<GetAccountAuthorizationDetailsR
         <Arn>{{ role.arn }}</Arn>
         <RoleName>{{ role.name }}</RoleName>
         <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-        <CreateDate>{{ role.create_date }}</CreateDate>
+        <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
         <RoleId>{{ role.id }}</RoleId>
       </member>
     {% endfor %}
@@ -1788,15 +1788,15 @@ GET_ACCOUNT_AUTHORIZATION_DETAILS_TEMPLATE = """<GetAccountAuthorizationDetailsR
             <Document>{{ policy_version.document }}</Document>
             <IsDefaultVersion>{{ policy_version.is_default }}</IsDefaultVersion>
             <VersionId>{{ policy_version.version_id }}</VersionId>
-            <CreateDate>{{ policy_version.create_datetime }}</CreateDate>
+            <CreateDate>{{ policy_version.created_iso_8601 }}</CreateDate>
           </member>
         {% endfor %}
         </PolicyVersionList>
         <Arn>{{ policy.arn }}</Arn>
         <AttachmentCount>1</AttachmentCount>
-        <CreateDate>{{ policy.create_datetime }}</CreateDate>
+        <CreateDate>{{ policy.created_iso_8601 }}</CreateDate>
         <IsAttachable>true</IsAttachable>
-        <UpdateDate>{{ policy.update_datetime }}</UpdateDate>
+        <UpdateDate>{{ policy.updated_iso_8601 }}</UpdateDate>
       </member>
     {% endfor %}
     </Policies>