## Issue description
When creating a CloudFormation stack, the `CreationDate` is always `2011-05-23T15:47:44Z`

## Steps to reproduce
1. Prepare a CloudFormation file, for example
```yml
AWSTemplateFormatVersion: 2010-09-09
Description: My Stack
Resources:
  LambdaCodeBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-bucket
```
2. Create a new stack based on this file, I used the command:
```bash
awslocal cloudformation create-stack --stack-name gch --template-body file://stack.yml
```
3. List all the created stacks and confirm the `CreationDate` is not a present date
```
awslocal cloudformation list-stacks
```
```
{
    "StackSummaries": [
        {
            "StackId": "arn:aws:cloudformation:us-east-1:000000000000:stack/stack/27187f13-a645-40a0-8788-62d502358216",
            "StackName": "stack",
            "TemplateDescription": "My Stack",
            "CreationTime": "2011-05-23T15:47:44Z",
            "StackStatus": "CREATE_COMPLETE"
        }
    ]
}
```
updated_item = find_existing_item(update_request, table_name)
                if not updated_item:
                    return
                new_record = clone(record)
                new_record['eventName'] = 'MODIFY'
                new_record['dynamodb']['Keys'] = keys
                new_record['dynamodb']['OldImage'] = self._thread_local('existing_items')[i]
                new_record['dynamodb']['NewImage'] = updated_item
                new_record['eventSourceARN'] = aws_stack.dynamodb_table_arn(table_name)
                records.append(new_record)
            delete_request = request.get('Delete')
            if delete_request:
                table_name = delete_request['TableName']
                keys = delete_request['Key']
                if isinstance(keys, Response):
                    return keys
                new_record = clone(record)
                new_record['eventName'] = 'REMOVE'
                new_record['dynamodb']['Keys'] = keys
                new_record['dynamodb']['OldImage'] = self._thread_local('existing_items')[i]
                new_record['eventSourceARN'] = aws_stack.dynamodb_table_arn(table_name)
                records.append(new_record)
        return records
    def _thread_local(self, name, default=None):
        try:
            return getattr(ProxyListenerDynamoDB.thread_local, name)
        except AttributeError:
            return default
UPDATE_DYNAMODB = ProxyListenerDynamoDB()
def find_existing_item(put_item, table_name=None):