## 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"
        }
    ]
}
```
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)
                i += 1
        return records
    def prepare_transact_write_item_records(self, record, data):
        records = []
        for i, request in enumerate(data['TransactItems']):
            put_request = request.get('Put')
            if put_request:
                existing_item = self._thread_local('existing_items')[i]
                table_name = put_request['TableName']
                keys = dynamodb_extract_keys(item=put_request['Item'], table_name=table_name)
                if isinstance(keys, Response):
                    return keys
                new_record = clone(record)
                new_record['eventName'] = 'INSERT' if not existing_item else 'MODIFY'
                new_record['dynamodb']['Keys'] = keys
                new_record['dynamodb']['NewImage'] = put_request['Item']
                if existing_item:
                    new_record['dynamodb']['OldImage'] = existing_item
                new_record['eventSourceARN'] = aws_stack.dynamodb_table_arn(table_name)
                records.append(new_record)
            update_request = request.get('Update')
            if update_request:
                table_name = update_request['TableName']
                keys = update_request['Key']
                if isinstance(keys, Response):
                    return keys